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BMR Calculator: Basal Metabolic Rate
Find out how much energy your body uses at rest. We show three well-known formulas side by side so you can see how much they disagree.
What BMR is
Basal Metabolic Rate is the energy your body needs at complete rest to run breathing, circulation, temperature control and cell repair. For most adults it makes up roughly 60% to 70% of daily energy use. It is not the number of calories you should eat. It is the floor that your activity sits on top of.
The three formulas
| Formula | Equation (W kg, H cm, A years) |
|---|---|
| Mifflin-St Jeor (1990) | Men: 10W + 6.25H − 5A + 5 Women: 10W + 6.25H − 5A − 161 |
| Revised Harris-Benedict (1984) | Men: 13.397W + 4.799H − 5.677A + 88.362 Women: 9.247W + 3.098H − 4.330A + 447.593 |
| Katch-McArdle | 370 + 21.6 × lean body mass (kg) |
Worked example: a man aged 30, 180 cm, 80 kg. Mifflin-St Jeor: 800 + 1,125 − 150 + 5 = 1,780 kcal.
Which formula should you trust?
- Most adults: Mifflin-St Jeor. It performed best in validation studies and is widely used by dietitians.
- Lean or muscular people who know their body fat: Katch-McArdle, because it uses lean mass. Enter your body fat above to see it.
- Harris-Benedict: shown for comparison. It can over-estimate in modern populations.
Pick one and keep using it. Switching formulas between weeks makes your tracking meaningless.
How to use your BMR
- Treat BMR as a baseline, not a target. Do not eat below it for long without supervision.
- Convert it into a daily target with the calorie calculator.
- Recalculate after every 5 kg change in weight.
- Remember that muscle, hormones, thyroid conditions and medications can move your real BMR away from the estimate.
Medical disclaimer: This tool is for education and general planning. It is not medical advice and does not diagnose any condition. If you are pregnant, under 18, have an eating-disorder history or a medical condition, speak to a doctor or registered dietitian before changing your diet or exercise.
Frequently asked questions
What is a normal BMR?
It depends on age, sex, height and weight. Typical adult values fall between about 1,200 and 2,000 kcal per day.
Can I raise my BMR?
Building muscle raises it slightly, and losing weight lowers it. Large increases from supplements or tricks are not supported by evidence.
BMR or RMR: what is the difference?
BMR is measured under strict resting conditions; RMR (resting metabolic rate) is measured more casually and is usually a little higher. Prediction equations estimate either.
Why do the formulas give different numbers?
They were built from different groups of people in different decades, and Katch-McArdle uses lean mass rather than total weight.
Is BMR the same as calories to lose weight?
No. Use your TDEE, then subtract for a deficit. See the calorie calculator.
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References and sources
- Mifflin MD, St Jeor ST, et al. (1990). A new predictive equation for resting energy expenditure in healthy individuals. Am J Clin Nutr 51:241-247. Link
- Roza AM, Shizgal HM (1984). The Harris Benedict equation reevaluated. Am J Clin Nutr 40:168-182.
- McArdle WD, Katch FI, Katch VL. Exercise Physiology: Energy, Nutrition, and Human Performance (Katch-McArdle formula).