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BMR Calculator

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Your BMR is the energy your body uses at complete rest just to stay alive: breathing, circulation, keeping warm and repairing cells. For most adults it's 1,200–2,000 kcal a day, about 60–70% of everything you burn. Enter your details to compare three standard equations.

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The three BMR equations

Mifflin-St Jeor (1990) Men: 10 × kg + 6.25 × cm − 5 × age + 5 Women: 10 × kg + 6.25 × cm − 5 × age − 161 Harris-Benedict (revised 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 (kg)
  • Mifflin-St Jeor is recommended by the American Academy of Nutrition and Dietetics as the most accurate for most adults, typically within 10% of measured values.
  • Harris-Benedict is the classic formula from 1919, updated in 1984. It tends to give slightly higher results.
  • Katch-McArdle uses lean body mass instead of weight, so it can be more accurate for very lean or very muscular people, if you know your body fat percentage.

BMR, RMR and TDEE

BMR (basal metabolic rate) is measured under strict conditions: fully rested, fasted, in a comfortable temperature. RMR (resting metabolic rate) is measured more loosely and is usually slightly higher; the terms are often used interchangeably. TDEE (total daily energy expenditure) adds activity and digestion on top, and is the number to use for planning how much to eat.

What affects your BMR

  • Body size and muscle: bigger bodies and more muscle burn more.
  • Age: BMR falls gradually with age, mostly because of lost muscle.
  • Sex: men usually have more muscle and a higher BMR at the same weight.
  • Hormones and health: thyroid conditions, illness and some medicines change BMR.
  • Severe dieting can lower it, one reason crash diets backfire.

Can you raise your BMR?

Building muscle through strength training is the most effective way. Eating enough protein and sleeping well help preserve muscle during weight loss. "Metabolism-boosting" foods and supplements have tiny effects at best.

Frequently asked questions

What is a normal BMR?

Most adult women have a BMR of about 1,200–1,500 kcal a day and men 1,500–1,900 kcal, depending on size, age and muscle.

Which BMR formula is most accurate?

Mifflin-St Jeor is the most accurate general formula. Katch-McArdle can be better if you know your body fat percentage accurately.

Should I eat my BMR in calories?

No. BMR is only the energy used at rest. To maintain weight you need your TDEE, which is BMR multiplied by your activity level.

Does BMR decrease with age?

Yes, slowly, mostly because muscle mass declines. Strength training helps slow this.

How can I measure my BMR exactly?

Clinics and some gyms measure it with indirect calorimetry, which analyses the oxygen you breathe in and the carbon dioxide you breathe out.

Last updated October 2026 · More health & fitness calculators