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BMR Calculator (Mifflin-St Jeor)

Estimate your basal metabolic rate — the calories your body burns at rest — from age, sex, height, and weight, in metric or imperial units.

BMR (calories/day)
1,649

How it works

This uses the Mifflin-St Jeor equation, the formula most current clinical nutrition guidance recommends over the older Harris-Benedict equation for estimating resting energy expenditure in healthy adults. For men: BMR = 10×weight(kg) + 6.25×height(cm) − 5×age(years) + 5. For women: BMR = 10×weight(kg) + 6.25×height(cm) − 5×age(years) − 161.

The formula's coefficients are calibrated for kilograms and centimeters, so imperial entries are converted to metric before the calculation runs and the result comes out identical either way.

BMR is the energy your body needs at complete rest just to keep functioning — breathing, circulation, cell repair — not counting any activity. It's the starting point for estimating total daily calorie needs, which multiplies BMR by an activity factor.

FAQ

Why is BMR lower for women than men at the same height and weight?

The Mifflin-St Jeor equation subtracts a larger constant for women (161 vs. adding 5 for men), reflecting that women's bodies typically carry a higher proportion of fat to lean mass than men's at the same height and weight, and fat tissue burns fewer calories at rest than muscle does.

Is this the same as how many calories I should eat?

No — BMR is calories burned at complete rest, not a target intake. Total daily calorie needs (sometimes called TDEE) multiply BMR by an activity factor to account for movement and exercise on top of resting metabolism.

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