BMR formulas
Mifflin-St Jeor (1990)
Women: 10W + 6.25H − 5A − 161
Revised Harris-Benedict (Roza & Shizgal, 1984)
Women: 447.593 + 9.247W + 3.098H − 4.330A
Katch-McArdle
W is weight in kilograms, H height in centimeters and A age in years.
What influences BMR
- Body size and composition — larger bodies and more muscle burn more energy.
- Age — BMR falls by roughly 1–2% per decade after early adulthood.
- Sex — men usually have a higher BMR because of greater lean mass.
- Genetics, hormones and health — thyroid function in particular has a large effect.
Equations estimate average BMR; an individual’s measured value can differ by 10% or more. Only indirect calorimetry measures it directly.
How to use the calculator
- Enter your age and sex.
- Enter your height and weight in U.S. or metric units.
- If you know your body fat percentage, add it to see the Katch-McArdle estimate, which uses lean body mass.
- Read your BMR from each formula and your daily calorie needs at different activity levels.
How BMR changes with age (Mifflin-St Jeor, kcal/day)
| Age | Man, 178 cm, 80 kg | Woman, 165 cm, 65 kg |
|---|---|---|
| 20 | 1,818 | 1,420 |
| 30 | 1,768 | 1,370 |
| 40 | 1,718 | 1,320 |
| 50 | 1,668 | 1,270 |
| 60 | 1,618 | 1,220 |
| 70 | 1,568 | 1,170 |
The formula subtracts 5 kcal per year of age. Much of the real-world decline comes from losing muscle, which strength training can slow.
Which formula is most accurate?
A review by the American Dietetic Association (Frankenfield et al., 2005) found that the Mifflin-St Jeor equation predicted resting metabolic rate within 10% of measured values in more healthy adults than other common equations, and it is the default here. The Harris-Benedict equation, first published in 1918 and revised in 1984, tends to give slightly higher values. Katch-McArdle can be better for very lean or muscular people, but only if body fat is measured accurately. Even the best equation can be off by 10% or more for an individual; a lab test using indirect calorimetry measures it directly.
BMR, RMR and TDEE
- BMR (basal metabolic rate): energy used at complete rest, measured under strict conditions after fasting and sleep.
- RMR (resting metabolic rate): measured under less strict conditions; usually slightly higher. The formulas here estimate it, and the terms are often used interchangeably.
- TDEE (total daily energy expenditure): BMR plus activity, exercise and the energy used to digest food. For most people BMR is 60–75% of TDEE.
Can you raise your BMR?
Muscle burns more energy at rest than fat — roughly 13 kcal per kg of muscle a day versus about 4.5 kcal per kg of fat. Gaining 2 kg of muscle therefore adds only about 25 kcal a day to BMR; the bigger benefit of strength training comes from the activity itself, better insulin sensitivity and preserving muscle during weight loss. Very low calorie diets can reduce BMR beyond what weight loss alone explains (adaptive thermogenesis), which is one reason moderate deficits are recommended. Sleep loss, thyroid disorders and some medications also affect metabolic rate.