Calorie calculator — BMR, maintenance and targets
Estimate how many calories you burn in a day. The calculator works out basal metabolic rate with the Mifflin-St Jeor equation, multiplies it by an activity factor to give total daily energy expenditure, and then shows the intake that corresponds to losing or gaining weight at a chosen rate. Every figure is an estimate for a population average, not a measurement of you.
How to use the Calorie Calculator
- Enter sex, age, height and weight — units can be metric or imperial.
- Pick the activity level that matches a typical week, not your best week.
- Choose a goal, or leave it on maintain.
- Press Estimate calories to see BMR, maintenance and the target intake.
The equation
Basal metabolic rate — the energy your body uses at complete rest — is estimated with the Mifflin-St Jeor equation, published by Mifflin, St Jeor and colleagues in the American Journal of Clinical Nutrition in 1990 (volume 51, pages 241–247):
Men: BMR = 10 × weight(kg) + 6.25 × height(cm) − 5 × age + 5
Women: BMR = 10 × weight(kg) + 6.25 × height(cm) − 5 × age − 161
Worked example: a 32-year-old woman of 165 cm and 68 kg gets 10 × 68 + 6.25 × 165 − 5 × 32 − 161 = 680 + 1,031.25 − 160 − 161 = 1,390 kcal a day at rest. Lightly active (×1.375) gives a maintenance estimate of 1,912 kcal.
Mifflin-St Jeor was developed as a replacement for the older Harris-Benedict equations, which tend to overestimate for modern populations. It is the equation most commonly recommended for non-obese and obese adults alike, and it typically lands within about 10% of measured resting expenditure — which is a wide band in practice.
Activity multipliers
| Multiplier | Describes |
|---|---|
| 1.2 | Sedentary — desk work, little deliberate exercise |
| 1.375 | Light — one to three sessions a week |
| 1.55 | Moderate — three to five sessions a week |
| 1.725 | Very active — six or seven sessions a week |
| 1.9 | Extra active — physical job, or training twice a day |
People routinely pick a level too high. Choose the one that matches an average week over a month, including the weeks you skip.
Deficits and surpluses
The conventional approximation is that a kilogram of body tissue is worth roughly 7,700 kcal (about 3,500 kcal per pound), so losing 0.5 kg a week implies a deficit of about 550 kcal a day. That arithmetic is a linear model of a non-linear process: as you lose weight your BMR falls, so the same intake produces a smaller deficit over time, and rates slow. Recalculate every few kilograms.
Limits — read this part
These are estimates from a population equation. They do not know your body composition, thyroid function, medication, sleep, genetics or how accurately you log food — and lean mass, not weight, drives most of the variation in resting expenditure, so the equation flatters neither very muscular nor very sedentary bodies. Most clinical guidance advises against dropping below roughly 1,200 kcal a day for women or 1,500 for men without medical supervision, because it becomes difficult to meet micronutrient needs. Do not use this calculator during pregnancy or breastfeeding, for children or teenagers, or if you have or are recovering from an eating disorder. If in doubt, speak to a GP or a registered dietitian.
Frequently asked questions
What is the Mifflin-St Jeor equation?
A 1990 equation for estimating basal metabolic rate from weight, height, age and sex. It is generally more accurate for modern populations than the older Harris-Benedict formulas.
What is the difference between BMR and TDEE?
BMR is what you burn at complete rest. TDEE is BMR multiplied by an activity factor, covering everything you actually do in a day — it is the figure to compare your intake against.
How big a deficit should I use?
A deficit of roughly 500 kcal a day corresponds to about 0.5 kg a week. Larger deficits are harder to sustain and make nutritional adequacy more difficult.
Why did my weight loss stall?
A smaller body burns fewer calories, so the same intake gives a smaller deficit as you lose. Recalculate after every few kilograms rather than sticking to the original number.
Privacy
This tool runs entirely inside your browser using WebAssembly and the Canvas/File APIs. Your files are never uploaded to ToolFlint or any third party; you can verify this in your browser's network tab or by switching to airplane mode after the page loads. Read how we process files.
Last updated 2026-09-23.