Find your Basal Metabolic Rate — the calories your body burns while resting.
The Mifflin-St Jeor equation, using weight (W, kg), height (H, cm) and age (A).
Men: 10W + 6.25H − 5A + 5
Women: 10W + 6.25H − 5A − 161
Your basal metabolic rate is the energy your body burns at complete rest to keep you alive: breathing, circulation, brain activity, temperature control and cell repair. This calculator estimates BMR in kilocalories per day using the Mifflin-St Jeor equation from your weight, height, age and sex.
BMR is the foundation of every calorie plan. On its own it is lower than what you need in a day, because it ignores movement and digestion, but multiplying it by an activity factor gives your total daily energy expenditure. Dietitians, fitness trainers and people planning to lose, gain or maintain weight start here. It also explains why two people eating the same food can have different results: a larger, taller or younger body burns more at rest.
1. Note weight in kg, height in cm and age in years.
2. Compute 10 × weight.
3. Compute 6.25 × height.
4. Compute 5 × age.
5. Add the first two, subtract the third: base = 10W + 6.25H − 5A.
6. For men add 5; for women subtract 161. The result is BMR in kcal/day.
The equation was published in 1990 by Mifflin, St Jeor and colleagues after measuring resting energy use in several hundred healthy adults and fitting a line to weight, height, age and sex. Later reviews found it predicts measured resting energy within about 10% for most healthy adults, better on average than the older Harris-Benedict equation from 1919. It is still an estimate built from averages, so an individual can be well above or below it.
The weight term adds 10 kcal for every kilogram, reflecting the energy cost of maintaining tissue. The height term adds 6.25 kcal per cm, because taller people have larger organs and more surface area. The age term subtracts 5 kcal per year, capturing the gradual loss of muscle and slower metabolism with age. The sex constant, +5 for men and −161 for women, accounts for average differences in body composition, mainly muscle mass.
Strictly, BMR is measured after an overnight fast, fully at rest in a warm room. Resting metabolic rate, RMR, is measured less strictly and is slightly higher. Mifflin-St Jeor actually predicts resting energy, and the two terms are used interchangeably in practice. Because muscle burns more energy than fat, two people with the same weight but different body fat can have different real BMRs. Formulas based on lean body mass, such as Katch-McArdle, can suit very muscular people better.
Rekha, a 41-year-old school teacher in Kolkata, weighs 58 kg and is 162 cm tall, and wants her resting calorie needs before planning her meals.
Answer: BMR 1,227 kcal/day
Treating BMR as the number of calories to eat, when daily needs are higher because of activity.
Eating below BMR for long periods without medical supervision.
Entering height in feet or inches instead of centimetres.
Expecting the formula to be exact for very muscular, very lean or very heavy people.
Forgetting to update the calculation after a large change in weight or with age.
The starting point for calculating TDEE and a calorie target.
Understanding how weight, age and height affect energy needs.
Planning diets for weight loss, maintenance or muscle gain.
Teaching metabolism in biology, nutrition and sports science classes.
Why is the formula different for men and women?
On average, men and women have different body makeup, especially muscle mass, which affects how many calories you burn at rest. The formula's fixed number accounts for this average difference.