Weight Loss Calculator
Set a goal weight and either a weekly rate or a target date, and get a daily calorie target from your TDEE, the number of weeks to your goal and a projected weight curve.
How to Use
- Choose By rate to pick a weekly loss (0.25, 0.5 or 1 kg, or 0.5, 1 or 2 lb), or By date to type a target date (YYYY-MM-DD) or a span such as 12 weeks.
- Pick your sex and enter your age, height, current weight and goal weight. Weights take kg, lb or stone (11 st 7 lb works); height takes cm, m, inches or 5'10.
- Choose your activity level; it sets the multiplier that turns your BMR into maintenance calories.
- Read your daily calorie target, the weeks to your goal and the daily deficit. The chart shows the straight-line rule and the slower curve when your energy needs are re-estimated as you lose.
- Check the message under the buttons: it flags a target below your BMR or a rate faster than 2 lb a week.
Worked Example
Losing 10 kg at 0.5 kg a week. A lightly active man, 35, 180 cm, 95 kg. BMR = 10 × 95 + 6.25 × 180 − 5 × 35 + 5 = 1,905 kcal; TDEE = 1,905 × 1.375 = 2,619 kcal. The deficit is 0.5 × 7,700 ÷ 7 = 550 kcal a day, so the target is 2,069 kcal a day, and 10 kg ÷ 0.5 kg = 20 weeks.
The same plan with TDEE re-estimated. If he keeps eating 2,069 kcal, his BMR falls by 10 kcal for every kilogram lost, so the deficit shrinks from 550 kcal towards about 413 kcal by the time he reaches 85 kg. Re-estimating week by week, he gets there in about 23 weeks, not 20.
The common mistake: treating the rule as exact. The 3,500 kcal per pound (7,700 kcal per kg) figure predicts a straight line. Real weight loss curves: the deficit gets smaller as you get lighter, and the body adapts in other ways too. Plan with the straight line, expect the curve, and recalculate every few kilograms.
Show Work
Formulas
From the 3,500-Calorie Rule to Dynamic Models
The rule that a pound of body weight is worth 3,500 kcal comes from Max Wishnofsky’s 1958 paper on the caloric equivalent of gained or lost weight. In metric terms it is about 7,700 kcal per kilogram. It is a fair estimate of the energy in fat tissue, and it is still the usual way to turn a weekly goal into a daily deficit.
Its weakness is that it assumes the deficit stays the same. In 2011 Kevin Hall and colleagues at the US National Institutes of Health published a mathematical model of human body weight in The Lancet showing why weight loss slows over time, and it became the basis of the NIH Body Weight Planner. This calculator does not reproduce that model; its second curve only re-estimates your Mifflin–St Jeor TDEE as your weight changes, which captures the largest effect in a simple way.
About This Tool
This calculator turns a goal weight and a weekly rate or a target date into a daily calorie target, the weeks needed and the date you would reach your goal, and draws two projected weight curves: the straight 7,700 kcal per kg rule and the same intake with your energy needs re-estimated as you lose. It flags targets below your BMR and rates faster than the 1–2 lb a week the CDC describes as gradual. For maintenance calories alone, use the TDEE Calculator.
Everything runs in your browser; nothing you enter is sent anywhere. For general information only — not medical advice. Talk to a doctor or other qualified professional about your own health.
Related tools: TDEE Calculator, BMI Calculator, and Body Fat Calculator.
Frequently Asked Questions
How is the daily calorie target worked out?
From your maintenance calories minus a daily deficit. A lightly active 35-year-old man, 180 cm and 95 kg, has a Mifflin–St Jeor BMR of 1,905 kcal and a TDEE of 1,905 × 1.375 = 2,619 kcal. Losing 0.5 kg a week needs 0.5 × 7,700 ÷ 7 = 550 kcal a day less, so about 2,069 kcal a day; 10 kg takes 20 weeks.
Is 3,500 kcal per pound (7,700 per kg) accurate?
It is an approximation from the 1950s that treats the deficit as fixed. As you lose weight your energy needs fall, so the same intake gives a smaller deficit. For the man above, re-estimating his TDEE week by week stretches 20 weeks to about 23. The dynamic model of Hall and colleagues at the US National Institutes of Health (2011) goes further and also models how the body adapts.
How fast should I lose weight?
The CDC says people who lose about 1 to 2 pounds a week at a gradual, steady pace are more likely to keep the weight off than people who lose it faster. 0.5 kg a week is 1.1 lb; 1 kg a week is 2.2 lb, just above that range, and the calculator notes it when you choose it.
What if my target comes out below my BMR?
The calculator flags it. A sedentary 40-year-old woman, 5 ft 5 in, going from 180 lb to 160 lb at 1 lb a week would need 1,285 kcal a day, below her BMR of 1,487 kcal. At 0.5 lb a week her target is about 1,535 kcal instead. Very-low-calorie diets should be medically supervised.
Can I plan for a date instead of a rate?
Yes. Choose By date and type a date or a span. A moderately active 30-year-old woman, 165 cm, going from 75 kg to 70 kg in 12 weeks needs 5 ÷ 12 = 0.417 kg a week, a deficit of 458 kcal a day, and a target of about 1,821 kcal.
How do I use the Weight Loss Calculator?
Simply type your numbers and read the result, which refreshes the instant you change something. There is nothing to submit and nothing to wait for.
Does it cost anything or need an account?
No. The tool is completely free, there is no account to create, and it keeps working offline after the page first loads.
Is anything I type uploaded?
No. The tool works entirely on your device, so the values you enter never leave your browser.
Common Use Cases
A steady plan
A sedentary 50-year-old man, 175 cm, losing 6 kg from 88 kg at 0.25 kg a week eats about 1,800 kcal for 24 weeks.
Stone and pounds
A moderately active 28-year-old woman, 163 cm, going from 11 st 7 lb to 10 st 7 lb at 0.5 kg a week eats about 1,694 kcal for 12.7 weeks.
Working back from an event
Type 12 weeks to see the rate and calories needed to reach a goal by a fixed day.
Gaining weight
A goal above your current weight gives a surplus: 65 kg to 70 kg at 0.25 kg a week for a moderately active 22-year-old man is about 2,844 kcal a day for 20 weeks.
Setting expectations
Compare the straight-line rule with the re-estimated curve: 20 weeks becomes about 22.6 for a 20 lb loss at 1 lb a week.
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