Useful Utilities

BMR Calculator

Estimate your basal metabolic rate with the Mifflin–St Jeor and Harris–Benedict equations from age, height and weight, and see how the standard activity multipliers scale it.

Fill in the values and calculate

SexBoth equations split by sexDefault Male
Age (years)*Age at last birthday, in years — required
Height (cm) (cm)Height in centimetres, shoes offDefault 170
Weight (kg) (kg)Current weight in kilogramsDefault 70

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About BMR Calculator

Basal metabolic rate is what your body burns per day at total rest — the floor for any daily food budget. This calculator runs both published formulas. Mifflin–St Jeor: BMR = 10 × mass(kg) + 6.25 × height(cm) − 5 × age + 5 for men, and the same terms with − 161 for women; it was developed in the 1970s after the Harris–Benedict equation was found to overestimate modern populations. Harris–Benedict: 66.5 + 13.75 × mass + 5.003 × height − 6.75 × age for men and 655.1 + 9.563 × mass + 1.850 × height − 4.676 × age for women.

The two answers typically differ by a few percent; nutrition professionals today prefer Mifflin–St Jeor, and this tool treats it as the primary number while still showing Harris–Benedict so you can see the gap. The activity table previews how daily energy requirements (TDEE) scale with exercise habits: sedentary ×1.2, lightly active ×1.375, moderately active ×1.55, very active ×1.725 and extremely active ×1.9. For your own maintenance figure, use the dedicated TDEE calculator.

BMR is measured in kilocalories per day at rest: neutral thermal environment, no digestion cost of food, no activity. It is a floor, not a goal — active people maintain well above it, and the number is an estimate from anthropometric formulas, with a few percent of individual error.

Questions about BMR Calculator

Which BMR formula is best?

Mifflin–St Jeor. It is the modern correction to the Harris–Benedict equation, which was built in 1948 and systematically reads a few percent high for average modern adults. This calculator shows both so you can judge the spread yourself.

How do I turn BMR into what I eat?

Multiply BMR by an activity factor: roughly ×1.2 for sedentary, ×1.375 light, ×1.55 moderate, ×1.725 very and ×1.9 extreme. The product is your estimated daily maintenance level (TDEE); the table above shows it pre-computed for your BMR.

Why is a woman's BMR formula so different?

Women carry proportionally more body fat and a smaller frame, so Harris–Benedict gave women their own coefficients (a +655 constant instead of +66.5). Mifflin–St Jeor only shifts by a constant: +5 for men, −161 for women.

Can BMR change with age?

Yes, but gently. Both equations lower BMR by roughly 5 kcal/day per year of age (6.75 in Harris–Benedict), a small correction relative to the mass and height terms.

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