Weight Loss Calculator
Find your daily calorie target, the weeks to your goal weight and your weight loss percentage. Plan with intermittent or water fasting, extra steps, cutting soda, or GLP-1 medicine. Free, with a safety check built in.
🧮 1. Weight Loss Calculator
Inputs
Your Result
___
Calculate first, then download your result as a plain text file.
📊 2. Your Weight Loss Results and Weight Loss Chart
Your calculation, step by step
Full results table
Table 2.1 Weight loss percentage chart: what each level means
| Level | Weight loss % | From 90 kg (198 lb) | What it means for health |
|---|---|---|---|
| Early progress You | Under 3% | Under 2.7 kg | Often mostly water at first. Keep going; the habits matter more than the number. |
| Noticeable You | 3% to 4.9% | 2.7 to 4.4 kg | Clothes start to fit differently. Blood sugar and triglycerides may begin to improve. |
| Clinically meaningful You | 5% to 9.9% | 4.5 to 8.9 kg | Linked to lower blood sugar, blood pressure and triglycerides, and lower diabetes risk. |
| Major You | 10% to 14.9% | 9 to 13.4 kg | Larger gains in blood pressure, cholesterol, liver fat and sleep apnoea. |
| Large You | 15% or more | 13.5 kg or more | Range seen with GLP-1 medicines or surgery. Can put type 2 diabetes into remission for some. |
After you press Calculate, your row turns dark green with a You badge. In Goal Plan mode it marks the total percentage you plan to lose. Health effects are from Wing et al. (2011) and Jensen et al. (2014).
Table 2.2 Body weight percentage loss calculator table: kg to lose for 5%, 10%, 15% and 20%
| Starting weight | 5% loss | 10% loss | 15% loss | 20% loss |
|---|---|---|---|---|
| 60 kg (132 lb) | 3.0 kg (6.6 lb) | 6.0 kg (13.2 lb) | 9.0 kg (19.8 lb) | 12.0 kg (26.5 lb) |
| 70 kg (154 lb) | 3.5 kg (7.7 lb) | 7.0 kg (15.4 lb) | 10.5 kg (23.1 lb) | 14.0 kg (30.9 lb) |
| 80 kg (176 lb) | 4.0 kg (8.8 lb) | 8.0 kg (17.6 lb) | 12.0 kg (26.5 lb) | 16.0 kg (35.3 lb) |
| 90 kg (198 lb) | 4.5 kg (9.9 lb) | 9.0 kg (19.8 lb) | 13.5 kg (29.8 lb) | 18.0 kg (39.7 lb) |
| 100 kg (220 lb) | 5.0 kg (11.0 lb) | 10.0 kg (22.0 lb) | 15.0 kg (33.1 lb) | 20.0 kg (44.1 lb) |
| 110 kg (243 lb) | 5.5 kg (12.1 lb) | 11.0 kg (24.3 lb) | 16.5 kg (36.4 lb) | 22.0 kg (48.5 lb) |
| 120 kg (265 lb) | 6.0 kg (13.2 lb) | 12.0 kg (26.5 lb) | 18.0 kg (39.7 lb) | 24.0 kg (52.9 lb) |
| 130 kg (287 lb) | 6.5 kg (14.3 lb) | 13.0 kg (28.7 lb) | 19.5 kg (43.0 lb) | 26.0 kg (57.3 lb) |
| 140 kg (309 lb) | 7.0 kg (15.4 lb) | 14.0 kg (30.9 lb) | 21.0 kg (46.3 lb) | 28.0 kg (61.7 lb) |
What to conclude: 5% of your starting weight is a smaller number than most people expect. At 100 kg it is only 5 kg, and that is enough to start seeing health benefits.
Table 2.3 TDEE weight loss calculator chart: calories a day to lose 0.5 kg a week
| Weight | Woman, sedentary | Woman, light | Woman, moderate | Man, sedentary | Man, light | Man, moderate |
|---|---|---|---|---|---|---|
| 60 kg | 1,200* | 1,231 | 1,458 | 1,500* | 1,571 | 1,841 |
| 70 kg | 1,200* | 1,368 | 1,613 | 1,500* | 1,708 | 1,996 |
| 80 kg | 1,244 | 1,506 | 1,768 | 1,541 | 1,846 | 2,151 |
| 90 kg | 1,364 | 1,643 | 1,923 | 1,661 | 1,983 | 2,306 |
| 100 kg | 1,484 | 1,781 | 2,078 | 1,781 | 2,121 | 2,461 |
| 110 kg | 1,604 | 1,918 | 2,233 | 1,901 | 2,258 | 2,616 |
| 120 kg | 1,724 | 2,056 | 2,388 | 2,021 | 2,396 | 2,771 |
Age 35. Women 165 cm, men 178 cm. Mifflin-St Jeor × activity, minus 550 kcal. A star (*) means the 1,200 or 1,500 kcal safety floor was applied, so the real pace is slower than 0.5 kg a week. What to conclude: lighter, less active people have much less room for a deficit, so adding activity matters more for them.
Table 2.4 How long does it take to lose weight? Weeks by pace
| Weight to lose | 0.25 kg a week | 0.5 kg a week | 0.75 kg a week | 1 kg a week |
|---|---|---|---|---|
| 2 kg (4 lb) | 8 weeks (1.8 months) | 4 weeks (0.9 months) | 3 weeks (0.6 months) | 2 weeks (0.5 months) |
| 5 kg (11 lb) | 20 weeks (4.6 months) | 10 weeks (2.3 months) | 7 weeks (1.5 months) | 5 weeks (1.2 months) |
| 10 kg (22 lb) | 40 weeks (9.2 months) | 20 weeks (4.6 months) | 13 weeks (3.1 months) | 10 weeks (2.3 months) |
| 15 kg (33 lb) | 60 weeks (13.8 months) | 30 weeks (6.9 months) | 20 weeks (4.6 months) | 15 weeks (3.5 months) |
| 20 kg (44 lb) | 80 weeks (18.4 months) | 40 weeks (9.2 months) | 27 weeks (6.1 months) | 20 weeks (4.6 months) |
| 25 kg (55 lb) | 100 weeks (23.0 months) | 50 weeks (11.5 months) | 33 weeks (7.7 months) | 25 weeks (5.8 months) |
| 30 kg (66 lb) | 120 weeks (27.6 months) | 60 weeks (13.8 months) | 40 weeks (9.2 months) | 30 weeks (6.9 months) |
Assumes you lower calories as you lose so the pace holds. Without adjusting, add about 15 to 25%. What to conclude: 10 kg at the recommended pace takes about 5 months, not 5 weeks.
Table 2.5 Steps calculator for weight loss: calories burned by extra steps
| Body weight | 5,000 extra steps | 10,000 extra steps | Weekly loss at 10,000 a day | Extra steps a day for 0.5 kg a week |
|---|---|---|---|---|
| 60 kg | 105 kcal | 211 kcal | 0.19 kg | 26,100 |
| 70 kg | 123 kcal | 246 kcal | 0.22 kg | 22,400 |
| 80 kg | 140 kcal | 281 kcal | 0.26 kg | 19,600 |
| 90 kg | 158 kcal | 316 kcal | 0.29 kg | 17,400 |
| 100 kg | 176 kcal | 351 kcal | 0.32 kg | 15,700 |
| 110 kg | 193 kcal | 386 kcal | 0.35 kg | 14,200 |
| 120 kg | 211 kcal | 421 kcal | 0.38 kg | 13,100 |
Height 170 cm, average pace (stride about 70 cm, 10,000 steps = 7.0 km). Net walking cost 0.5 kcal per kg per km. What to conclude: steps help most when paired with a modest calorie cut, because walking alone needs very high step counts to lose 0.5 kg a week.
Table 2.6 Fasting weight loss calculator chart: protocols compared
| Plan | How it works | Example intake | Example result | What the evidence says |
|---|---|---|---|---|
| 16:8 | Eat within 8 hours, fast 16 | 1,700 kcal a day | 4.3 kg in 12 weeks | Similar to daily calorie cutting when calories match (Lowe et al., 2020) |
| 18:6 or 20:4 | Eat within 6 or 4 hours | Depends on intake | Same rule: the deficit decides | Shorter window can make eating less easier |
| OMAD | One meal a day | 1,500 kcal a day | 4.4 kg in 8 weeks | Hard to get enough protein and fiber in one meal |
| 5:2 | 2 days at 500 to 600 kcal, 5 normal days | 2,000 kcal normal days, avg 1,571 | 5.6 kg in 12 weeks | Similar weight loss to daily restriction in trials |
| Alternate-day | 500 kcal every other day | Average of the two days | Depends on feast days | Same loss as daily restriction, more dropouts (Trepanowski et al., 2017) |
| Water fast | No food, water only, 1 to 3 days | 0 kcal | 2.9 kg on the scale in 3 days, 0.9 kg fat | Mostly water; needs medical advice, supervision past 3 days |
Examples use a 35-year-old woman, 165 cm, 85 kg, lightly active (maintenance 2,125 kcal), except the water fast (man, 80 kg). What to conclude: pick the fasting style you can keep up. The calorie gap, not the clock, sets the result.
Table 2.7 GLP-1 weight loss calculator chart: average results in major trials
| Medicine | Trial | Length | Average loss | Placebo | From 100 kg |
|---|---|---|---|---|---|
| Semaglutide 2.4 mg weekly | STEP 1 | 68 weeks | 14.9% | 2.4% | 14.9 kg |
| Tirzepatide 15 mg weekly | SURMOUNT-1 | 72 weeks | 20.9% | 3.1% | 20.9 kg |
| Tirzepatide 10 mg weekly | SURMOUNT-1 | 72 weeks | 19.5% | 3.1% | 19.5 kg |
| Tirzepatide 5 mg weekly | SURMOUNT-1 | 72 weeks | 15.0% | 3.1% | 15.0 kg |
| Liraglutide 3.0 mg daily | SCALE | 56 weeks | 8.0% | 2.6% | 8.0 kg |
| Phentermine/topiramate 15/92 mg | CONQUER | 56 weeks | 9.8% | 1.2% | 9.8 kg |
| Phentermine 15 mg | Aronne 2013 | 28 weeks | 6.1% | 1.7% | 6.1 kg |
Averages from the published trials, where both groups also had diet and activity advice. Prescription only. Doses are set by a doctor, and this page gives no dosing advice. What to conclude: GLP-1 medicines produced two to four times the loss of older options, but individual results vary widely.
Table 2.8 Quitting soda weight loss calculator: small swaps over a year
| Habit change | kcal saved a day | Fat equivalent in 30 days | Fat equivalent in 1 year |
|---|---|---|---|
| Quit 1 can of regular soda a day | 140 kcal | 0.5 kg | 6.6 kg (14.6 lb) |
| Quit 2 cans of regular soda a day | 280 kcal | 1.1 kg | 13.3 kg (29.3 lb) |
| Quit 1 large sugary coffee drink a day | 250 kcal | 1.0 kg | 11.9 kg (26.1 lb) |
| Swap a 250 kcal snack for fruit (about 80 kcal) | 170 kcal | 0.7 kg | 8.1 kg (17.8 lb) |
| Walk 30 minutes more a day (85 kg, about 4,000 steps) | 115 kcal | 0.4 kg | 5.5 kg (12.0 lb) |
| Cut 1 tablespoon of oil a day | 120 kcal | 0.5 kg | 5.7 kg (12.5 lb) |
Uses 7,700 kcal per kg. Real loss over a year is smaller because your body adapts and burns less as you get lighter (Hall et al., 2011). What to conclude: one daily swap can be worth several kilograms a year, as long as the calories are not eaten back elsewhere.
Visualisations
Chart 1 shows your weight over time. Chart 2 breaks your result into its parts.
1. Your projected weight
Weight over time for your plan
2. Breakdown
What makes up your result
⚡ Quick Answer: How Do You Calculate Weight Loss?
A weight loss calculator finds your maintenance calories (TDEE), subtracts a safe daily deficit, and divides the weight you want to lose by your weekly pace.
Rule of thumb: a 550 kcal daily gap loses about 0.5 kg a week. For a 35-year-old, 85 kg woman, that means about 1,575 kcal a day and 26 weeks to lose 13 kg.
Key Takeaways
- A weight loss calculator needs your sex, age, height, weight and activity to estimate maintenance calories.
- A daily gap of about 550 kcal loses roughly 0.5 kg (1.1 lb) a week; 1,100 kcal loses about 1 kg.
- Your weight loss percentage is (start − current) ÷ start × 100, and 5% is the first health milestone.
- Safe limits: no more than 1 kg or 1% of body weight a week, and no less than 1,200 kcal (women), 1,500 kcal (men) or 1,800 kcal (breastfeeding).
- Fasting, steps and GLP-1 medicines all work through the same calorie gap; a 3-day water fast drops about 3 kg on the scale but only about 1 kg of fat.
📚 3. What Is a Weight Loss Calculator?
A weight loss calculator is a tool that turns your body size and daily habits into a plan: how many calories to eat, how fast you will lose, and when you will reach your goal weight. It works on energy balance. When you take in fewer calories than you burn, your body uses stored fat to cover the gap.
This calculator does five jobs in one page. The Goal Plan tab works as a TDEE weight loss calculator and a macros calculator for weight loss. The Percent Lost tab is a weight loss percentage calculator. The Fasting tab covers intermittent fasting, OMAD and water fasting. The Steps and Habits tab shows what extra walking or quitting soda is worth. The GLP-1 and Medication tab compares your weight with average trial results for semaglutide, tirzepatide, liraglutide and phentermine.
A worked one-liner: a 35-year-old woman who is 165 cm, 85 kg and lightly active burns about 2,125 kcal a day. Eating 1,575 kcal leaves a 550 kcal gap, which is 0.5 kg a week, so losing 13 kg takes about 26 weeks.
Who uses it: people starting a diet who want a realistic date, people tracking progress who want their weight loss percentage, dietitians and coaches who need a quick estimate, and people on prescribed weight loss medicine who want to know what is typical. Researchers report weight change as a percentage because 5 kg means more to a 70 kg person than to a 140 kg person.
For a second opinion on long timelines, the NIH Body Weight Planner uses a more detailed model of how metabolism adapts. The CDC guide to losing weight recommends a gradual pace of about 0.5 to 1 kg (1 to 2 lb) a week.
| Tool | What it tells you | Use it when |
|---|---|---|
| Weight loss calculator | Calorie target, weeks to goal, % lost | You want a plan with a date |
| TDEE calculator | Calories you burn to stay the same | You only need maintenance calories |
| BMI calculator | Weight relative to height | You want to know if your weight is in a healthy range |
| Body fat percentage | How much of you is fat | You lift weights and BMI misreads you |
| Macro calculator | Grams of protein, carbs and fat | You already know your calorie target |
🧠 4. What Does Your Weight Loss Result Mean?
4.1 What your calorie target really is
Your calorie target is an average to aim for, not a number you must hit every day. If you eat 200 kcal over on Saturday and 200 under on Sunday, the week still balances. Track the weekly average and your weight trend, not single days.
4.2 Why the scale moves faster in week 1
Most people lose 1 to 2 kg in the first week of a diet, which is faster than the plan says. This is stored glycogen and the water bound to it, not fat. From week 2 the pace settles near the number the calculator shows. Do not judge the plan on the first week alone.
4.3 Why weight loss slows down
A lighter body burns fewer calories, so the same intake gives a smaller gap each week. The calculator shows this as two timelines: one where you lower your calories a little as you lose, and one where you never change them. Hall et al. (2011) showed the old "3,500 kcal per pound" rule overpredicts loss for this reason. Re-run the calculator every 4 to 5 kg.
4.4 What a good weight loss percentage looks like
Use Table 2.1. Losing 5% is the first big milestone. In the Look AHEAD trial, people who lost 5 to 10% had clear improvements in blood sugar, blood pressure and blood fats, and those who lost 10 to 15% did better still (Wing et al., 2011). A weekly pace of 0.5 to 1% of body weight is steady and safe for most adults.
4.5 Why the safety floor changes your plan
If your target falls below 1,200 kcal (women), 1,500 kcal (men) or 1,800 kcal (breastfeeding), the calculator raises it to that floor and makes the plan slower. Very low calorie diets make it hard to get enough protein, vitamins and minerals, and they need medical supervision. Adding steps is a safer way to speed things up.
4.6 What fasting results mean
Time-restricted eating such as 16:8 or OMAD only causes weight loss if it leads you to eat fewer calories. Trials find it works about as well as plain calorie cutting (Lowe et al., 2020; Trepanowski et al., 2017). A water fast drops the scale fast, but most of that drop is water that returns when you eat again.
4.7 What GLP-1 and medication projections mean
The projection is the average from a large trial. Half of people did better and half did worse. People also had diet and activity advice in those trials. Weight usually returns when the medicine stops, so ask your doctor about the long-term plan.
4.8 What to do next
- Write down your calorie target and protein goal, and plan two or three meals that fit them.
- Weigh yourself at the same time 2 to 7 times a week and look at the weekly average.
- Add steps before you cut calories further.
- Re-run the calculator after every 4 to 5 kg lost, or every 6 to 8 weeks.
- See a doctor or dietitian if you have a health condition or take medicine.
4.9 Common mistakes this calculator prevents
- Picking an unsafe pace. Requests above 1 kg or 1% a week are capped.
- Eating too little. Targets below the safety floor are raised.
- Setting an underweight goal. Goals with a BMI under 18.5 get no plan.
- Counting water as fat. The fasting tab separates water from fat loss.
- Mixing units. The percentage formula uses one unit for both weights, and unit changes convert your numbers exactly.
✍ 5. How to Use Your Result
📌 Tips
- Save it in your phone notes so you can check it at the shop.
- Share it with a friend who will check in with you.
📌 Tips
- Bring a list of your medicines.
- Ask about blood tests before and after a 5% loss.
- Ask whether any medicine needs a dose change as you lose weight.
📌 Tips
- Plan protein first at each meal.
- Keep easy, filling foods at home: vegetables, beans, eggs, yogurt, lean meat.
📌 Tips
- Measure your waist at the navel, breathing out.
- Compare weekly averages, not single days.
📌 Tips
- Use this in a coaching log, school project or clinical note.
- Name the formula and the date you calculated.
∑ 6. What Is the Weight Loss Formula?
These are the exact formulas this weight loss calculator uses. Every number on the page comes from one of them.
📝 7. How to Use This Weight Loss Calculator
- Pick a tab. Goal Plan for a calorie target and date, Percent Lost for progress, Fasting, Steps and Habits, or GLP-1 and Medication.
- Choose your units. Kilograms or pounds, and centimetres, feet and inches, or inches. Switching converts what you typed.
- Enter sex, age and height. For example: female, 35 years, 165 cm.
- Enter your current weight. Weigh in the morning before eating. Example: 85 kg.
- Enter your goal weight. Example: 72 kg. Goals under a BMI of 18.5 are not planned.
- Pick your activity level honestly. Example: lightly active (1.375). Most people overestimate this.
- Choose a weekly pace or a number of weeks. Example: 0.5 kg a week. Faster requests are capped.
- Press Calculate. The result panel shows about 1,575 kcal a day, a steady pace on the gauge, and 26 weeks to goal.
- Read Section 2. See your macros (118 g protein on the balanced split), the week-by-week table, and where you sit in Table 2.1.
- Save it. Use Download TXT, Download Doc or Download PDF, or copy a card from Section 5.
📈 8. How Do You Calculate Weight Loss Percentage in Excel?
Excel handles every part of this weight loss calculator with plain formulas. No add-ins or the Analysis ToolPak are needed. The worked example below is the same woman used across the page: 35 years, 165 cm, 85 kg, goal 72 kg, lightly active, 0.5 kg a week.
=(A2-B2)/A2 and format the cell as a percentage. That is your weight loss percentage.8.1 The formulas you need
| You want | Excel formula | Note |
|---|---|---|
| Weight loss percentage | =(A2-B2)/A2 | Format as %, or multiply by 100 |
| BMR, woman | =10*B2+6.25*B3-5*B4-161 | Use +5 instead of -161 for a man |
| TDEE | =B8*B6 | BMR times activity factor |
| Calorie target with safety floor | =MAX(1200,B9-B7*7700/7) | Use 1500 for men, 1800 if breastfeeding |
| Weeks to goal | =(B2-B5)/B7 | Weight to lose divided by pace |
| Goal date | =TODAY()+ROUNDUP(B12*7,0) | Format the cell as a date |
| 5% target weight | =A2*0.95 | Use 0.90 for 10% |
| Protein grams (30%) | =B11*0.30/4 | Fat uses /9 instead of /4 |
8.2 Step by step
1 Enter your numbers in column B
Put a label in column A and the value in column B, one item per row. Keep weights in kg and height in cm. If you work in pounds, convert first with =B2*0.45359237.
Weight 85, height 165, age 35, goal 72, activity 1.375 and pace 0.5 sit in B2:B7.
2 Calculate BMR and TDEE
=10*B2+6.25*B3-5*B4-161=B8*B6The first formula is the Mifflin-St Jeor equation for a woman. The second multiplies it by your activity factor.
BMR is 1545.25 kcal and TDEE is 2124.72 kcal, the same as the calculator.
3 Find your calorie target, weeks and goal date
=B7*7700/7=MAX(1200,B9-B7*7700/7)=(B2-B5)/B7MAX applies the safety floor so the target never drops below 1,200 kcal.
Deficit 550, target 1575 kcal (1,574.72 unrounded), 26 weeks. The goal date shown assumes you start on October 16, 2026.
4 Track your weight loss percentage
=(A2-B2)/A2Put each weigh-in on a new row and fill the formula down. Format column C as a percentage with 2 decimal places.
85 to 80 kg is 5.88%; 90 to 85.5 kg is exactly 5.00%.
8.3 The awkward cases
- Pounds and stones: convert to kg first. 1 lb = 0.45359237 kg, 1 stone = 6.35029318 kg.
- Feet and inches:
=(feet*12+inches)*2.54gives cm. - A weight gain: the formula returns a negative percentage. Wrap it as
=MAX(0,(A2-B2)/A2)if you only want losses. - Men: change -161 to +5 in BMR and 1200 to 1500 in the floor.
=(A2-B2)/A2*100 and then also format the cell as a percentage, Excel shows 588% instead of 5.88%. Do one or the other, not both.8.4 Why answers can differ between Excel, R, Python and this page
They should agree to the calorie. Small differences come from rounding: Excel's ROUND rounds 0.5 away from zero, while R's round() and Python's round() round 0.5 to the nearest even number. This page rounds only for display. Goal dates can differ by a day if one tool counts the start day and another does not.
8.5 Charting your progress
Select the week and weight columns, then choose Insert, Line chart. Add a horizontal line at your goal by adding a column filled with the goal weight. A trendline (right-click the series, Add Trendline, Linear) shows your average weekly loss as its slope.
8.6 Error messages
#DIV/0!: the starting weight or pace cell is empty or zero.#VALUE!: a cell holds text such as "85kg". Type the number only.#####: the column is too narrow for a date. Widen it.#NAME?: a typo in a function name, such asMAXX.
These formulas work the same in Google Sheets. TODAY() and ROUNDUP behave identically.
📈 9. How Do You Calculate a Weight Loss Plan in R?
This script is a complete weight loss calculator in R. It prints the BMR, TDEE, calorie target, weeks to goal and weight loss percentage, then saves one 300 dpi chart. It uses base R only, so there is nothing to install.
Rscript. Change only the numbers in part 1.9.1 The complete script
R, base only, saves weight_loss_plan.png
# ============================================================
# Weight loss calculator in R (matches statsunlock.com)
# Mifflin-St Jeor BMR, activity factor, 7,700 kcal per kg
# ============================================================
# ---- 1. Your numbers (change only these lines) -------------
sex <- "female" # "female" or "male"
age <- 35 # years
height <- 165 # cm
weight <- 85 # kg, today
goal <- 72 # kg
activity <- 1.375 # 1.2, 1.375, 1.55, 1.725 or 1.9
rate <- 0.5 # kg per week you want to lose
# Or read your weigh-ins from a file:
# df <- na.omit(read.csv("weights.csv"))
# ---- 2. BMR and TDEE ----------------------------------------
bmr <- function(w) 10 * w + 6.25 * height - 5 * age + ifelse(sex == "male", 5, -161)
tdee <- bmr(weight) * activity
# ---- 3. Safe pace and calorie target ------------------------
max_rate <- min(1.0, 0.01 * weight)
rate <- min(rate, max_rate)
deficit <- rate * 7700 / 7
floor_k <- ifelse(sex == "male", 1500, 1200)
target <- tdee - deficit
if (target < floor_k) {
target <- floor_k
deficit <- tdee - floor_k
rate <- deficit * 7 / 7700
}
weeks <- (weight - goal) / rate
# ---- 4. What if you never change calories? ------------------
w <- weight; history <- weight
while (w > goal && length(history) < 520) {
gap <- bmr(w) * activity - target
if (gap <= 0) break
w <- w - gap * 7 / 7700
history <- c(history, w)
}
# ---- 5. Weight loss percentage ------------------------------
pct_to_lose <- (weight - goal) / weight * 100
cat(sprintf("BMR: %.2f kcal\n", bmr(weight)))
cat(sprintf("TDEE: %.2f kcal\n", tdee))
cat(sprintf("Daily target: %.0f kcal (deficit %.0f)\n", target, deficit))
cat(sprintf("Pace: %.2f kg per week\n", rate))
cat(sprintf("Weeks to goal: %.1f\n", weeks))
cat(sprintf("Never adjusting: %d weeks\n", length(history) - 1))
cat(sprintf("Weight to lose: %.2f%% of body weight\n", pct_to_lose))
cat("Verdict: eat about", round(target), "kcal a day and re-check every 4 to 5 kg.\n")
# ---- 6. One figure, 300 dpi ---------------------------------
x <- 0:(length(history) - 1)
plan <- pmax(goal, weight - rate * x)
png("weight_loss_plan.png", width = 7, height = 4, units = "in", res = 300)
plot(x, plan, type = "l", lwd = 2.5, col = "#16a34a", ylim = range(c(plan, history)),
xlab = "Week", ylab = "Weight (kg)", main = "Weight loss plan")
lines(x, history, lwd = 2, lty = 2, col = "#f59e0b")
abline(h = goal, lty = 3, col = "#64748b")
legend("topright", c("Calories re-set as you lose", "Calories never changed"),
col = c("#16a34a", "#f59e0b"), lwd = 2, lty = c(1, 2), bty = "n")
dev.off()9.2 What each part does
| Part | What it does |
|---|---|
| bmr() | Mifflin-St Jeor equation as a function of weight, so it can be re-run as weight falls |
| max_rate | Caps the pace at 1 kg or 1% of body weight a week |
| floor_k | Safety floor: 1,200 kcal for women, 1,500 for men |
| while loop | Week-by-week simulation when calories are never changed |
| png(..., res = 300) | Saves the chart at print quality |
9.3 What the output shows
For the example it prints BMR 1545.25, TDEE 2124.72, a target of 1575 kcal, 26.0 weeks with calories re-set, 32 weeks if never changed, and 15.29% of body weight to lose. The chart draws both timelines with the goal as a dotted line.
9.4 Problems and fixes
- Error in png(): on a server without graphics, add
type = "cairo". - Loop never ends: it stops at 520 weeks; if it does, your target is close to maintenance at the goal weight.
- Wrong sex: the text must be exactly "male" or "female".
9.5 One-liners
Quick R checks
(85 - 80) / 85 * 100 # weight loss percentage: 5.88
(10*85 + 6.25*165 - 5*35 - 161) * 1.375 - 550 # target: 1574.72
(85 - 72) / 0.5 # weeks to goal: 26
85 * c(0.95, 0.90, 0.85) # 5, 10, 15% targets📈 10. How Do You Calculate Weight Loss Percentage in Python?
This Python script matches the calculator to the calorie. It prints the full plan and the weight loss percentage, and saves a 300 dpi chart with Matplotlib.
Install once with pip install numpy matplotlib.
10.1 The complete script
Python 3, saves weight_loss_plan.png
# ============================================================
# Weight loss calculator in Python (matches statsunlock.com)
# Mifflin-St Jeor BMR, activity factor, 7,700 kcal per kg
# ============================================================
import numpy as np
import matplotlib
matplotlib.use("Agg") # save the figure without a screen
import matplotlib.pyplot as plt
# ---- 1. Your numbers (change only these lines) -------------
sex = "female" # "female" or "male"
age = 35 # years
height = 165 # cm
weight = 85 # kg, today
goal = 72 # kg
activity = 1.375 # 1.2, 1.375, 1.55, 1.725 or 1.9
rate = 0.5 # kg per week you want to lose
# Or read your weigh-ins from a file:
# import pandas as pd; df = pd.read_csv("weights.csv").dropna()
# ---- 2. BMR and TDEE ----------------------------------------
def bmr(w, h=height, a=age, s=sex):
return 10 * w + 6.25 * h - 5 * a + (5 if s == "male" else -161)
tdee = bmr(weight) * activity
# ---- 3. Safe pace and calorie target ------------------------
max_rate = min(1.0, 0.01 * weight) # never faster than this
rate = min(rate, max_rate)
deficit = rate * 7700 / 7
floor = 1500 if sex == "male" else 1200 # safety floor
target = tdee - deficit
if target < floor:
target = floor
deficit = tdee - floor
rate = deficit * 7 / 7700
weeks = (weight - goal) / rate
# ---- 4. What if you never change calories? ------------------
w, history = weight, [weight]
while w > goal and len(history) < 520:
gap = bmr(w) * activity - target
if gap <= 0:
break
w -= gap * 7 / 7700
history.append(w)
# ---- 5. Weight loss percentage ------------------------------
pct_to_lose = (weight - goal) / weight * 100
print(f"BMR: {bmr(weight):.2f} kcal")
print(f"TDEE: {tdee:.2f} kcal")
print(f"Daily target: {target:.0f} kcal (deficit {deficit:.0f})")
print(f"Pace: {rate:.2f} kg per week")
print(f"Weeks to goal: {weeks:.1f}")
print(f"Never adjusting: {len(history) - 1} weeks")
print(f"Weight to lose: {pct_to_lose:.2f}% of body weight")
print("Verdict: eat about", round(target), "kcal a day and re-check every 4 to 5 kg.")
# ---- 6. One figure, 300 dpi ---------------------------------
x = np.arange(0, len(history))
plan = np.maximum(goal, weight - rate * x)
plt.figure(figsize=(7, 4))
plt.plot(x, plan, color="#16a34a", lw=2.5, label="Calories re-set as you lose")
plt.plot(x, history, color="#f59e0b", lw=2, ls="--", label="Calories never changed")
plt.axhline(goal, color="#64748b", lw=1, ls=":")
plt.xlabel("Week"); plt.ylabel("Weight (kg)")
plt.title("Weight loss plan")
plt.legend(); plt.tight_layout()
plt.savefig("weight_loss_plan.png", dpi=300)10.2 What each part does
| Part | What it does |
|---|---|
| bmr(w) | Mifflin-St Jeor equation, re-run at each new weight |
| min(rate, max_rate) | Caps the pace at 1 kg or 1% of body weight a week |
| if target < floor | Raises the target to the safety floor and slows the pace |
| while w > goal | The calories-never-changed timeline |
| plt.savefig(dpi=300) | Saves the chart at print quality |
10.3 What the output shows
We ran this script for the example. It printed BMR 1545.25 kcal, TDEE 2124.72 kcal, a target of 1575 kcal with a 550 kcal deficit, 26.0 weeks to goal, 32 weeks if calories are never changed, and 15.29% of body weight to lose. These match the calculator exactly.
10.4 Problems and fixes
- ModuleNotFoundError: run
pip install numpy matplotlib. - No window opens: that is intended. The chart is saved as weight_loss_plan.png next to the script.
- Percent looks 100 times too small: you left out
* 100.
10.5 One-liners
Quick Python checks
(85 - 80) / 85 * 100 # 5.88
(10*85 + 6.25*165 - 5*35 - 161) * 1.375 - 550 # 1574.72
(85 - 72) / 0.5 # 26.0
[round(85 * f, 2) for f in (0.95, 0.90, 0.85)] # [80.75, 76.5, 72.25]📋 11. Weight Loss Reference Tables
11.1 Activity factors for TDEE
| Level | Factor | What it looks like | Steps a day (rough) |
|---|---|---|---|
| Sedentary | 1.2 | Desk job, little planned exercise | Under 5,000 |
| Lightly active | 1.375 | Exercise 1 to 3 days a week | 5,000 to 7,500 |
| Moderately active | 1.55 | Exercise 3 to 5 days a week | 7,500 to 10,000 |
| Very active | 1.725 | Hard exercise 6 to 7 days a week | 10,000 to 12,500 |
| Extra active | 1.9 | Physical job plus training | Over 12,500 |
What to conclude: if unsure, pick the lower level. Step ranges follow Tudor-Locke et al. (2011) and are a guide only.
11.2 Safety limits used by this calculator
| Group | Lowest daily target | Fastest weekly pace |
|---|---|---|
| Women | 1,200 kcal | 1 kg (2.2 lb) or 1% of body weight, whichever is lower |
| Men | 1,500 kcal | 1 kg (2.2 lb) or 1% of body weight, whichever is lower |
| Breastfeeding | 1,800 kcal | 0.5 kg (1.1 lb) |
| Under 18, pregnant, BMI under 18.5 | No plan is given. Please see a doctor. | |
Based on Jensen et al. (2014) and common clinical practice, as of 2026. What to conclude: targets below these levels need a doctor.
11.3 Macros calculator for weight loss: grams per day (protein / carbs / fat)
| Split | 1,400 kcal | 1,600 kcal | 1,800 kcal | 2,000 kcal |
|---|---|---|---|---|
| Balanced 30/40/30 | 105 / 140 / 47 | 120 / 160 / 53 | 135 / 180 / 60 | 150 / 200 / 67 |
| High protein 40/30/30 | 140 / 105 / 47 | 160 / 120 / 53 | 180 / 135 / 60 | 200 / 150 / 67 |
| Lower carb 35/25/40 | 122 / 88 / 62 | 140 / 100 / 71 | 158 / 112 / 80 | 175 / 125 / 89 |
| Keto 25/5/70 | 88 / 18 / 109 | 100 / 20 / 124 | 112 / 22 / 140 | 125 / 25 / 156 |
Protein and carbs give 4 kcal per gram, fat 9. What to conclude: on keto, carbs stay near 20 to 25 g a day; on the balanced split they are 140 to 200 g.
11.4 Calorie and protein calculator for weight loss: daily protein
| Body weight | 0.8 g/kg (minimum RDA) | 1.2 g/kg (weight loss low end) | 1.6 g/kg (weight loss high end) |
|---|---|---|---|
| 60 kg (132 lb) | 48 g | 72 g | 96 g |
| 70 kg (154 lb) | 56 g | 84 g | 112 g |
| 80 kg (176 lb) | 64 g | 96 g | 128 g |
| 90 kg (198 lb) | 72 g | 108 g | 144 g |
| 100 kg (220 lb) | 80 g | 120 g | 160 g |
| 110 kg (243 lb) | 88 g | 132 g | 176 g |
| 120 kg (265 lb) | 96 g | 144 g | 192 g |
Higher protein helps keep muscle and fullness while losing weight (Leidy et al., 2015). If you have kidney disease, ask your doctor first. What to conclude: most people losing weight should aim between the last two columns.
11.5 Fiber calculator for weight loss
| Calories eaten | Fiber target (14 g per 1,000 kcal) |
|---|---|
| 1,200 kcal | 17 g |
| 1,400 kcal | 20 g |
| 1,600 kcal | 22 g |
| 1,800 kcal | 25 g |
| 2,000 kcal | 28 g |
| 2,200 kcal | 31 g |
| 2,500 kcal | 35 g |
Source: Dietary Guidelines for Americans 2020 to 2025 adequate intake rule, as of 2026. What to conclude: even on a low calorie diet, aim for at least 17 to 22 g of fiber a day.
11.6 Healthy goal weight by height (BMI 18.5 to 24.9)
| Height | Lowest healthy weight | Top of healthy range | Top of overweight range |
|---|---|---|---|
| 150 cm (4 ft 11 in) | 41.6 kg | 56.0 kg | 67.3 kg |
| 155 cm (5 ft 1 in) | 44.4 kg | 59.8 kg | 71.8 kg |
| 160 cm (5 ft 3 in) | 47.4 kg | 63.7 kg | 76.5 kg |
| 165 cm (5 ft 5 in) | 50.4 kg | 67.8 kg | 81.4 kg |
| 170 cm (5 ft 7 in) | 53.5 kg | 72.0 kg | 86.4 kg |
| 175 cm (5 ft 9 in) | 56.7 kg | 76.3 kg | 91.6 kg |
| 180 cm (5 ft 11 in) | 59.9 kg | 80.7 kg | 96.9 kg |
| 185 cm (6 ft 1 in) | 63.3 kg | 85.2 kg | 102.3 kg |
| 190 cm (6 ft 3 in) | 66.8 kg | 89.9 kg | 107.9 kg |
World Health Organization adult BMI bands, as of 2026. What to conclude: any goal under the first column is refused by this calculator.
11.7 Breastfeeding weight loss calculator: calorie additions
| Stage | Extra calories a day | Floor used here | Pace limit |
|---|---|---|---|
| Exclusively breastfeeding, 0 to 6 months | +330 kcal | 1,800 kcal | 0.5 kg a week |
| Breastfeeding, 7 to 12 months | +400 kcal | 1,800 kcal | 0.5 kg a week |
| Pregnant | Do not use a weight loss plan. Ask your midwife or doctor. | ||
Values follow the Institute of Medicine dietary reference intakes, as of 2026. Gradual loss while breastfeeding does not harm milk supply in studies (Dewey et al., 1993). What to conclude: breastfeeding raises your calorie needs, so plans are slower.
📈 12. Weight Loss Calculator Examples
Eight worked examples, each checked against an independent re-calculation of the formulas.
A steady plan from 85 kg to 72 kg
The standard 0.5 kg a week plan, start to finish.
A 35-year-old woman, 165 cm, 85 kg, lightly active, wants to reach 72 kg. She chooses the recommended pace of 0.5 kg a week.
| Item | Value | Note |
|---|---|---|
| BMR | 1,545 kcal | Mifflin-St Jeor |
| TDEE | 2,125 kcal | BMR × 1.375 |
| Daily target | 1,575 kcal | 550 kcal deficit |
| Weeks (calories re-set) | 26 | 13 kg ÷ 0.5 |
| Weeks (calories never changed) | 32 | Slowdown |
| Protein | 118 g | Balanced split |
What it means: She should eat about 1,575 kcal a day. Her BMI falls from 31.2 to 26.4, and she passes the 5% milestone (80.75 kg) in about 9 weeks.
How to use it: Re-run the calculator at 80 kg and 76 kg. Her target at 72 kg will be about 1,396 kcal for the same pace.
A 20% weight loss percentage
How to calculate percentage of weight loss after a big change.
A man started at 110 kg and now weighs 88 kg after a year of diet changes.
| Item | Value | Note |
|---|---|---|
| Starting weight | 110 kg | Day 1 |
| Current weight | 88 kg | Today |
| Weight lost | 22 kg | 110 − 88 |
| Weight loss % | 20.00% | 22 ÷ 110 × 100 |
| 10% mark | 99 kg | Passed |
| 15% mark | 93.5 kg | Passed |
What it means: 20% puts him in the Large band of Table 2.1, the range usually seen with GLP-1 medicine or surgery. (BMI uses a height of 180 cm.)
How to use it: Focus on keeping it off: keep protein high, keep walking, and weigh in weekly so small regains are caught early.
A 2.14% loss after three weeks
A small number that is still real progress.
A woman started at 70 kg and weighs 68.5 kg after three weeks.
| Item | Value | Note |
|---|---|---|
| Starting weight | 70 kg | |
| Current weight | 68.5 kg | |
| Weight loss % | 2.14% | 1.5 ÷ 70 × 100 |
| 5% target | 66.5 kg | 2 kg to go |
| Pace so far | 0.5 kg a week | 1.5 ÷ 3 |
What it means: Some of the first weeks is water, so the real fat loss may be a little less than 1.5 kg. Her pace of 0.5 kg a week is right on target.
How to use it: Keep going. At this pace she reaches 5% (66.5 kg) in about 4 more weeks.
Exactly 5%: 90 kg down to 85.5 kg
Sitting right on the first health milestone.
A man started at 90 kg and now weighs 85.5 kg.
| Item | Value | Note |
|---|---|---|
| Weight lost | 4.5 kg | 90 − 85.5 |
| Weight loss % | 5.00% | 4.5 ÷ 90 × 100 |
| Band | Clinically meaningful | 5% counts as the start of this band |
| Next goal, 10% | 81 kg | 4.5 kg to go |
What it means: The 5 percent weight loss calculator line matters because trials found clear health gains from about 5% (Wing et al., 2011). One kilogram either side changes the band, so look at the trend over a few weeks.
How to use it: Tell your doctor at your next visit. Blood sugar, blood pressure and cholesterol may already be improving.
Asking for 1 kg a week on a small body
The calculator caps the pace and applies the safety floor.
A 58-year-old woman, 155 cm, 68 kg, sedentary, wants to lose 8 kg at 1 kg a week.
| Item | Value | Note |
|---|---|---|
| TDEE | 1,437 kcal | Small, sedentary, older |
| Asked for | 1 kg a week | 1,100 kcal gap |
| Safe cap | 0.68 kg a week | 1% of 68 kg |
| Target after floor | 1,200 kcal | Safety floor |
| Real pace | 0.22 kg a week | 237 kcal gap |
| Weeks to goal | 37 | 8 ÷ 0.216 |
What it means: Her maintenance is only about 1,437 kcal, so diet alone gives a small gap. The honest answer is 37 weeks, not 8.
How to use it: Add steps: 5,000 extra a day burns about 110 kcal for her and cuts the time by about a third. Strength training helps keep muscle.
A 3-day water fast: 2.9 kg on the scale
The big number is mostly water.
A 40-year-old man, 178 cm, 80 kg, lightly active, does a 3-day water fast and sees the scale drop by almost 3 kg.
| Item | Value | Note |
|---|---|---|
| Water and glycogen | 2.00 kg | 2.5% of 80 kg |
| Fat (upper estimate) | 0.92 kg | 2,362 × 3 ÷ 7,700 |
| Total scale drop | 2.92 kg | 3.65% of body weight |
| Likely back after eating | About 2 kg | The water part |
What it means: The water fast weight loss calculator shows why people "regain" right after a fast: the water comes back, the 0.9 kg of fat does not.
How to use it: The same 0.9 kg of fat comes off in about 14 days at a 500 kcal daily gap, with no fasting risks. Talk to a doctor before any water fast.
A goal weight below the healthy range
The calculator refuses to plan it.
A woman, 165 cm, 60 kg, enters a goal of 48 kg.
| Item | Value | Note |
|---|---|---|
| Current BMI | 22.0 | Already healthy |
| Goal BMI | 17.6 | 48 ÷ 1.65² |
| Lowest healthy weight | 50.4 kg | 18.5 × 1.65² |
| Result | Error message | No calories or dates shown |
What it means: A weight loss calculator should not help someone reach an underweight goal. The message names the lowest healthy weight for her height.
How to use it: If you are worried about your weight or eating, please talk to a doctor. In the US you can reach the National Alliance for Eating Disorders helpline.
6,000 extra steps and quitting 2 sodas
A steps calculator for weight loss in real life.
A woman, 165 cm, 85 kg, adds 6,000 steps a day and stops drinking two cans of regular cola.
| Item | Value | Note |
|---|---|---|
| Extra distance | 4.09 km | 6,000 × 0.68 m |
| Walking | 174 kcal | 0.5 × 85 × 4.09 |
| Soda cut | 280 kcal | 2 × 140 |
| Total a day | 454 kcal | |
| In 12 weeks | 4.95 kg | 5.8% of body weight |
What it means: Two small habits give about 5 kg in 12 weeks with no diet plan, if she does not eat more to make up for it.
How to use it: Start with the soda swap, which is easiest, then build up steps by 1,000 a week.
📏 13. How Do You Get Your Numbers Right?
Bad inputs cause most wrong answers. Follow these steps for an accurate result.
- Weigh yourself in the morning, after using the toilet and before eating or drinking.
- Use the same scale on a hard, flat floor, not a carpet.
- Wear the same light clothes, or none, every time.
- Measure height without shoes, heels against a wall, looking straight ahead. Mark the top of your head with a flat object.
- Use your age in whole years on your last birthday.
- Pick the lower activity level if you are between two. Most people overestimate.
- Count real eating-day calories for the fasting tab, using a food tracking app for a few days.
- Count only extra steps in the steps tab. Check your usual daily steps first.
- Use a weekly average for progress, because daily weight swings by 1 to 2 kg with water and salt.
- Measure your waist at the navel, breathing out, to track size changes the scale misses.
| Input | Unit | Typical adult range | Common mistake |
|---|---|---|---|
| Weight | kg or lb | 45 to 180 kg | Mixing kg and lb between start and current |
| Height | cm, ft + in, or in | 150 to 195 cm | Typing 5.5 for 5 ft 5 in (that is 5 ft 6 in) |
| Age | years | 18 to 100 | Using age next birthday |
| Activity | factor | 1.2 to 1.9 | Counting one gym visit as "very active" |
| Eating-day calories | kcal | 1,200 to 3,000 | Forgetting drinks, oils and snacks |
| Extra steps | steps a day | 2,000 to 10,000 | Entering total steps instead of extra steps |
✅ 14. When Should You Use a Weight Loss Calculator?
- You are an adult starting a diet and want a calorie target
- You want a realistic goal date
- You want your weight loss percentage
- You are comparing fasting, steps or medicine plans
- You want to check if your plan is safe
- You are under 18
- You are pregnant
- Your BMI is already under 18.5
- You have or had an eating disorder
- You have kidney disease, type 1 diabetes, or take insulin, without your doctor
Four examples
- New year plan: a man of 105 kg wants 90 kg. Goal Plan gives 2,229 kcal and 20 weeks.
- Progress check: a woman who went from 92 to 86.5 kg uses Percent Lost and sees 5.98%.
- New mother: breastfeeding at 4 months, she uses the breastfeeding option and gets the 1,800 kcal floor.
- Starting GLP-1: a patient wants to know what is typical before seeing the doctor.
Decision guide
| If you want | Use |
|---|---|
| A calorie target and goal date | Goal Plan tab |
| To know how much you have lost | Percent Lost tab |
| To know if your weight is healthy | A BMI calculator |
| A child or teen weight check | A doctor and CDC growth charts, not this tool |
| Long-term detail on metabolic slowdown | The NIH Body Weight Planner |
🔧 15. Troubleshooting and Common Errors
Why does another website give a different answer?
Cause: Other sites may use the Harris-Benedict or Katch-McArdle equation, 3,500 kcal per pound, different activity factors, or no safety floor.
Fix: This tool uses Mifflin-St Jeor (1990), 7,700 kcal per kg and the 1.2 to 1.9 activity scale. Expect differences of 100 to 200 kcal between equations.
I am losing slower than the calculator said.
Cause: Activity was set too high, calories are under-counted, or your metabolism has slowed as you lost weight.
Fix: Drop one activity level, track food for a week, and re-run the calculator at your new weight.
I lost much more in week 1.
Cause: Glycogen and water loss at the start of any diet.
Fix: Judge the plan from week 2 onward.
My target says "Safety floor".
Cause: Your planned target was below 1,200, 1,500 or 1,800 kcal.
Fix: Accept the slower plan, or add steps to widen the gap safely.
It says my goal is below the healthy range.
Cause: The goal gives a BMI under 18.5 for your height.
Fix: Choose a goal at or above the lowest healthy weight shown in Table 11.6.
The percentage looks wrong.
Cause: Start and current were entered in different units, or the wrong way round.
Fix: Use the same unit for both. Starting weight goes in the starting field.
Height in feet gives a strange result.
Cause: Typing 5.5 in the feet box means 5.5 feet, which is 5 ft 6 in.
Fix: Use the feet + inches option and put 5 and 5 in the two boxes.
My fasting plan shows no loss.
Cause: Your average intake is at or above maintenance.
Fix: Lower eating-day calories. The fasting window alone does not cause loss.
Charts do not appear.
Cause: The chart library could not load, often because of a blocker or no connection.
Fix: All numbers are still in the tables. Reload the page or allow cdnjs.cloudflare.com.
The Download buttons are grey.
Cause: They stay off until you press Calculate, and turn off again when you change mode, sample or units.
Fix: Press Calculate again.
⚠️ 16. Assumptions and Limitations
- Mifflin-St Jeor fits you. It is within 10% for most adults. If you are very muscular, it underestimates your burn, so the plan runs faster than shown. Better: Katch-McArdle with a measured body fat percentage.
- Your activity factor is right. Most people pick too high, so real loss is slower. Better: a few weeks of tracking, then adjust.
- 7,700 kcal per kg holds. Early loss includes water and some lean tissue, so week 1 is faster and later weeks slower. Better: the NIH Body Weight Planner for long horizons.
- Calories eaten are accurate. People under-report intake by 20 to 40% on average, so real loss is usually slower. Better: weigh food for a week.
- Adaptive slowdown is only partly modeled. The body can burn less than the equations predict after large losses (Rosenbaum and Leibel, 2010), so plans can stall. Better: re-run every 4 to 5 kg and add strength training.
- The water fast model is simple. Water and glycogen are set at 2.5% of body weight, and real values vary from 1 to 3 kg. Fat loss is an upper estimate. Better: a supervised program with medical monitoring.
- Steps use a fixed stride. Real stride varies by leg length and speed, so the error can be 10 to 15% either way. Better: measure distance with a phone or watch.
- Medicine projections are averages. Your result can be far above or below. Better: your doctor's monitoring.
🏁 17. Conclusion
Run the calculator above to add your own numbers to this conclusion. ___
A weight loss calculator gives you three things a guess cannot: a daily calorie target, a realistic date, and a way to measure progress as a percentage. For most adults, a gap of about 550 kcal a day loses 0.5 kg a week, and losing 5% of your starting weight is the first milestone that clearly helps your health.
Every method on this page, from 16:8 fasting to extra steps to GLP-1 medicine, works through the same calorie gap. Pick the one you can keep up. The safety limits are there because faster is not better: very low calories and very fast loss raise the risk of muscle loss, gallstones and regain.
Re-run the numbers every 4 to 5 kg, weigh in weekly, and talk to a doctor if you have a health condition. Used that way, this weight loss calculator turns a vague goal into a plan you can follow week by week.
❓ 18. Frequently Asked Questions
Q1. How does a weight loss calculator work?
A weight loss calculator estimates how many calories you burn each day, then sets a lower calorie target so you lose weight at a chosen pace. This one uses the Mifflin-St Jeor equation for resting burn, multiplies it by an activity factor, and uses about 7,700 kcal per kilogram of fat to turn the daily gap into weeks and a goal date.
Q2. How do I calculate my weight loss percentage?
Subtract your current weight from your starting weight, divide by your starting weight, then multiply by 100. If you started at 85 kg and now weigh 80 kg, you lost 5 kg, and 5 divided by 85 times 100 is 5.88%. Use the same unit, kg or lb, for both weights.
Q3. How many calories should I eat to lose weight?
Most adults lose about 0.5 kg (1 lb) a week by eating 500 to 550 kcal less than their maintenance calories. For a 35-year-old woman who is 165 cm, 85 kg and lightly active, that is about 1,575 kcal a day. Women should not go below 1,200 kcal and men below 1,500 kcal without medical supervision.
Q4. How long will it take to lose 10 kg?
At a steady 0.5 kg a week, losing 10 kg takes about 20 weeks, or roughly 5 months. At 1 kg a week it takes 10 weeks, but that pace is only safe for people with a higher starting weight. If you never lower your calories as you lose, expect it to take about 15 to 25% longer.
Q5. What is TDEE and how do I calculate it for weight loss?
TDEE, or total daily energy expenditure, is all the calories you burn in a day. Calculate your BMR with Mifflin-St Jeor, then multiply by an activity factor from 1.2 (sedentary) to 1.9 (extra active). To lose weight, eat less than your TDEE: a 550 kcal gap gives about 0.5 kg a week.
Q6. Is 3,500 calories really one pound of fat?
Roughly, yes, for the first few weeks. One pound of body fat holds about 3,500 kcal, and 1 kg holds about 7,700 kcal. But the simple rule overpredicts long-term loss, because your body burns less as you get lighter. That is why this calculator shows a second timeline where calories are never adjusted.
Q7. What is a good percentage of weight loss?
Losing 5% of your starting weight is the first big milestone, because it is linked to better blood sugar, blood pressure and blood fats. Losing 10% brings larger benefits, and 15% or more can improve sleep apnoea and fatty liver. A safe pace is 0.5 to 1% of body weight per week.
Q8. How much weight can you lose on a water fast?
Most people see the scale drop by about 1 kg a day for the first 2 or 3 days of a water fast, but much of that is water and stored glycogen. Real fat loss is only about 0.25 to 0.35 kg a day. Most of the water returns after normal eating. Fasts over 3 days need medical supervision.
Q9. Does intermittent fasting help you lose more weight?
Intermittent fasting works about as well as ordinary calorie cutting when total calories are the same. Trials of 16:8 and alternate-day fasting found similar weight loss to daily calorie restriction. It helps people who find it easier to skip meals than to eat smaller ones. The calorie gap, not the clock, decides the result.
Q10. How much weight can I lose with OMAD?
With OMAD (one meal a day) your loss depends on how many calories that meal holds. A 35-year-old, 85 kg woman eating 1,500 kcal in one meal would lose about 4.4 kg in 8 weeks. If the single meal is large enough to cover your maintenance calories, you will not lose weight.
Q11. How many steps a day do I need to lose weight?
Every 1,000 extra steps burns about 20 to 45 kcal, depending on your weight and stride. For an 85 kg person, 6,000 extra steps burn about 175 kcal a day, close to 0.16 kg a week. Losing 0.5 kg a week from walking alone would need about 19,000 extra steps, so combine steps with eating a little less.
Q12. How much weight will I lose if I quit soda?
A 355 ml (12 oz) can of regular cola has about 140 kcal. Cutting one can a day saves about 51,000 kcal a year, which is roughly 6.6 kg (14.6 lb) of body fat, as long as you do not replace it with other calories. Cutting two cans a day doubles that.
Q13. How much weight can you lose on GLP-1 medicines like semaglutide or tirzepatide?
In large trials, semaglutide 2.4 mg gave an average loss of 14.9% after 68 weeks, and tirzepatide 15 mg gave 20.9% after 72 weeks, against 2.4% and 3.1% on placebo. Results vary widely between people. Only a doctor can prescribe these medicines and decide the dose.
Q14. How much weight do people lose on phentermine?
In a 28-week trial, people taking phentermine 15 mg lost about 6% of their body weight on average, against 1.7% on placebo. Phentermine combined with topiramate gave about 9.8% after 56 weeks in the CONQUER trial. Phentermine is a prescription medicine and is usually used short term.
Q15. How many calories should I eat while breastfeeding to lose weight?
Breastfeeding burns roughly 330 extra kcal a day in the first 6 months and 400 kcal later. Most guidance says to eat at least 1,800 kcal a day and lose no more than about 0.5 kg a week, so milk supply is protected. This calculator applies both limits when you choose breastfeeding.
Q16. How much protein and fiber do I need to lose weight?
Aim for about 1.2 to 1.6 g of protein per kilogram of body weight while losing weight, which helps protect muscle and keeps you full. For fiber, aim for 14 g per 1,000 kcal you eat, so about 22 g on a 1,575 kcal diet. The calculator shows both for your plan.
Q17. How much weight do you need to lose to drop a pant size?
As a rough rule, men lose about 1 inch of waist for every 4 kg (9 lb) lost, and women drop about one clothing size for every 5 kg (11 lb). Where you store fat, your height and the brand all change this, so treat it as a guide and use a tape measure to track it.
Q18. How do I calculate weight loss percentage in Excel?
Put your starting weight in B2 and current weight in B3, then type =(B2-B3)/B2 in another cell and format it as a percentage. For a calorie target, use =10*B4+6.25*B5-5*B6-161 for a woman's BMR, multiply by the activity factor, and subtract =0.5*7700/7. Section 8 shows each step.
Q19. How do I calculate a weight loss plan in R?
Write a small function for Mifflin-St Jeor BMR, multiply by the activity factor to get TDEE, then subtract rate times 7700 divided by 7. In R, (start - current) / start * 100 gives the weight loss percentage. Section 9 has a complete script that prints the plan and saves a 300 dpi chart.
Q20. How do I calculate weight loss percentage in Python?
In Python, pct = (start - current) / start * 100 gives your weight loss percentage. For a full plan, compute BMR with Mifflin-St Jeor, multiply by the activity factor, and subtract the daily deficit. Section 10 has a complete script using NumPy and Matplotlib that matches this calculator to the calorie.
📑 19. Cite This Tool
StatsUnlock Team. (2026). Weight loss calculator [Interactive online tool]. StatsUnlock. https://statsunlock.com/weight-loss-calculator/@misc{statsunlock_weightloss_2026, title={Weight Loss Calculator}, author={{StatsUnlock Team}}, year={2026}, note={Interactive online tool}, url={https://statsunlock.com/weight-loss-calculator/}}Daily calorie targets were estimated with the StatsUnlock Weight Loss Calculator (2026), which uses the Mifflin-St Jeor equation with standard activity factors, an energy content of 7,700 kcal per kg, a maximum pace of 1 kg or 1% of body weight per week, and minimum intakes of 1,200 kcal (women), 1,500 kcal (men) and 1,800 kcal (breastfeeding). Percentage weight loss was calculated as (start minus current) divided by start, times 100.📖 21. Glossary of Terms
| Term | Plain-English meaning |
|---|---|
| Activity factor | A number from 1.2 to 1.9 that scales your resting burn up to your whole-day burn. |
| Alternate-day fasting | Eating normally one day and about 500 kcal the next, in turn. |
| BMI | Body mass index: weight in kg divided by height in metres squared. |
| BMR | Basal metabolic rate: calories you burn at complete rest in a day. |
| Calorie (kcal) | A unit of energy in food. Food labels say "calories" but mean kilocalories. |
| Calorie deficit | Eating fewer calories than you burn, so the body uses stored energy. |
| Fiber | The part of plant food you cannot digest. It keeps you full and helps digestion. |
| GLP-1 medicine | A prescription medicine, such as semaglutide, that copies a gut hormone to reduce appetite. |
| Glycogen | Stored carbohydrate in muscle and liver, held with water. It is used up first when you fast. |
| Intermittent fasting | Eating only in set time windows or on set days, such as 16:8 or 5:2. |
| Macros | Short for macronutrients: protein, carbohydrate and fat. |
| Maintenance calories | The calories that keep your weight the same. Same as TDEE. |
| Mifflin-St Jeor | The 1990 equation this page uses to estimate BMR from weight, height, age and sex. |
| OMAD | One meal a day: all food eaten in a single meal. |
| Placebo | A dummy treatment given in a trial, used to measure the real effect of a medicine. |
| Plateau | A period when weight stops falling even though you have not changed your habits. |
| Safety floor | The lowest daily calorie target this calculator will show. |
| TDEE | Total daily energy expenditure: all the calories you burn in a day. |
| Water fast | Taking only water, with no food, for a set time. |
| Weight loss percentage | Weight lost divided by starting weight, times 100. |
📚 22. References
These peer-reviewed sources support the formulas, safety limits and trial figures used in this weight loss calculator.
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- Dewey, K. G., Heinig, M. J., & Nommsen, L. A. (1993). Maternal weight-loss patterns during prolonged lactation. The American Journal of Clinical Nutrition, 58(2), 162–166. https://doi.org/10.1093/ajcn/58.2.162
- Finnell, J. S., Saul, B. C., Goldhamer, A. C., & Myers, T. R. (2018). Is fasting safe? A chart review of adverse events during medically supervised, water-only fasting. BMC Complementary and Alternative Medicine, 18, 67. https://doi.org/10.1186/s12906-018-2136-6
- Gadde, K. M., Allison, D. B., Ryan, D. H., Peterson, C. A., Troupin, B., Schwiers, M. L., & Day, W. W. (2011). Effects of low-dose, controlled-release, phentermine plus topiramate combination on weight and associated comorbidities in overweight and obese adults (CONQUER). The Lancet, 377(9774), 1341–1352. https://doi.org/10.1016/S0140-6736(11)60205-5
- Hall, K. D., Sacks, G., Chandramohan, D., Chow, C. C., Wang, Y. C., Gortmaker, S. L., & Swinburn, B. A. (2011). Quantification of the effect of energy imbalance on bodyweight. The Lancet, 378(9793), 826–837. https://doi.org/10.1016/S0140-6736(11)60812-X
- Jastreboff, A. M., Aronne, L. J., Ahmad, N. N., Wharton, S., Connery, L., Alves, B., et al. (2022). Tirzepatide once weekly for the treatment of obesity. New England Journal of Medicine, 387(3), 205–216. https://doi.org/10.1056/NEJMoa2206038
- Jensen, M. D., Ryan, D. H., Apovian, C. M., Ard, J. D., Comuzzie, A. G., Donato, K. A., et al. (2014). 2013 AHA/ACC/TOS guideline for the management of overweight and obesity in adults. Circulation, 129(25 Suppl 2), S102–S138. https://doi.org/10.1161/01.cir.0000437739.71477.ee
- Leidy, H. J., Clifton, P. M., Astrup, A., Wycherley, T. P., Westerterp-Plantenga, M. S., Luscombe-Marsh, N. D., Woods, S. C., & Mattes, R. D. (2015). The role of protein in weight loss and maintenance. The American Journal of Clinical Nutrition, 101(6), 1320S–1329S. https://doi.org/10.3945/ajcn.114.084038
- Lowe, D. A., Wu, N., Rohdin-Bibby, L., Moore, A. H., Kelly, N., Liu, Y. E., et al. (2020). Effects of time-restricted eating on weight loss and other metabolic parameters: The TREAT randomized clinical trial. JAMA Internal Medicine, 180(11), 1491–1499. https://doi.org/10.1001/jamainternmed.2020.4153
- Malik, V. S., Pan, A., Willett, W. C., & Hu, F. B. (2013). Sugar-sweetened beverages and weight gain in children and adults: A systematic review and meta-analysis. The American Journal of Clinical Nutrition, 98(4), 1084–1102. https://doi.org/10.3945/ajcn.113.058362
- Mifflin, M. D., St Jeor, S. T., Hill, L. A., Scott, B. J., Daugherty, S. A., & Koh, Y. O. (1990). A new predictive equation for resting energy expenditure in healthy individuals. The American Journal of Clinical Nutrition, 51(2), 241–247. https://doi.org/10.1093/ajcn/51.2.241
- Pi-Sunyer, X., Astrup, A., Fujioka, K., Greenway, F., Halpern, A., Krempf, M., et al. (2015). A randomized, controlled trial of 3.0 mg of liraglutide in weight management. New England Journal of Medicine, 373(1), 11–22. https://doi.org/10.1056/NEJMoa1411892
- Rosenbaum, M., & Leibel, R. L. (2010). Adaptive thermogenesis in humans. International Journal of Obesity, 34(Suppl 1), S47–S55. https://doi.org/10.1038/ijo.2010.184
- Thomas, D. M., Martin, C. K., Lettieri, S., Bredlau, C., Kaiser, K., Church, T., Bouchard, C., & Heymsfield, S. B. (2013). Can a weight loss of one pound a week be achieved with a 3500-kcal deficit? Commentary on a commonly accepted rule. International Journal of Obesity, 37(12), 1611–1613. https://doi.org/10.1038/ijo.2013.51
- Trepanowski, J. F., Kroeger, C. M., Barnosky, A., Klempel, M. C., Bhutani, S., Hoddy, K. K., et al. (2017). Effect of alternate-day fasting on weight loss, weight maintenance, and cardioprotection among metabolically healthy obese adults. JAMA Internal Medicine, 177(7), 930–938. https://doi.org/10.1001/jamainternmed.2017.0936
- Tudor-Locke, C., Craig, C. L., Brown, W. J., Clemes, S. A., De Cocker, K., Giles-Corti, B., et al. (2011). How many steps/day are enough? For adults. International Journal of Behavioral Nutrition and Physical Activity, 8, 79. https://doi.org/10.1186/1479-5868-8-79
- Varady, K. A., Cienfuegos, S., Ezpeleta, M., & Gabel, K. (2022). Clinical application of intermittent fasting for weight loss: Progress and future directions. Nature Reviews Endocrinology, 18(5), 309–321. https://doi.org/10.1038/s41574-022-00638-x
- Wilding, J. P. H., Batterham, R. L., Calanna, S., Davies, M., Van Gaal, L. F., Lingvay, I., et al. (2021). Once-weekly semaglutide in adults with overweight or obesity. New England Journal of Medicine, 384(11), 989–1002. https://doi.org/10.1056/NEJMoa2032183
- Wilhelmi de Toledo, F., Grundler, F., Bergouignan, A., Drinda, S., & Michalsen, A. (2019). Safety, health improvement and well-being during a 4 to 21-day fasting period in an observational study including 1422 subjects. PLOS ONE, 14(1), e0209353. https://doi.org/10.1371/journal.pone.0209353
- Wing, R. R., Lang, W., Wadden, T. A., Safford, M., Knowler, W. C., Bertoni, A. G., et al. (2011). Benefits of modest weight loss in improving cardiovascular risk factors in overweight and obese individuals with type 2 diabetes. Diabetes Care, 34(7), 1481–1486. https://doi.org/10.2337/dc10-2415
