BMR Calculator
Basal metabolic rate by three published equations, side by side.
How to use BMR Calculator
- Choose units and enter sex, age, weight and height.
- Optionally enter your body-fat percentage to add the Katch–McArdle result.
- Compare the three equations and see calories for each activity level.
How it works
Basal metabolic rate is the energy your body needs in a day at complete rest: breathing, circulation, temperature, cell repair. Three equations are shown. Mifflin–St Jeor (1990): 10 × kg + 6.25 × cm − 5 × age, +5 for men, −161 for women. Harris–Benedict as revised by Roza and Shizgal (1984): men 88.362 + 13.397 × kg + 4.799 × cm − 5.677 × age; women 447.593 + 9.247 × kg + 3.098 × cm − 4.330 × age. Katch–McArdle: 370 + 21.6 × lean body mass in kg, which needs your body-fat percentage and is the same for both sexes.
Mifflin–St Jeor is the headline figure because comparative studies found it closest to measured values for most adults. Katch–McArdle is used instead when you give body fat, because lean mass predicts resting energy better than total weight for lean or muscular people.
Example
A 40-year-old woman, 60 kg and 165 cm: Mifflin–St Jeor gives 600 + 1,031.25 − 200 − 161 = 1,270 kcal a day.
Frequently asked questions
What is a normal BMR?
It depends on size, age and sex. Most adult women fall around 1,200–1,600 kcal a day and most men around 1,500–2,000. Larger and more muscular bodies burn more; BMR falls slowly with age.
Which BMR formula is the most accurate?
For most adults, Mifflin–St Jeor. If you know your body-fat percentage and are lean or muscular, Katch–McArdle is usually closer.
Should I eat my BMR to lose weight?
No. BMR is what you burn lying still. Your real daily use is higher: see the activity table, or use the calorie calculator for a target.
Why do the formulas give different numbers?
They were fitted to different groups of people in different decades. A spread of 50–100 kcal is normal and well inside the accuracy of any of them.
Limitations
- Equations are population averages: individuals commonly differ by ±10%.
- Adults aged 15–100; not validated for children, pregnancy or illness.
- An estimate for healthy adults, not medical advice. Talk to a doctor or registered dietitian about your own situation.
Last reviewed November 9, 2026. How we build and test tools.