BMR Calculator
What your body burns at rest, and what a day actually costs.
Reading your result
Fill in every field and the steps will be spelled out here.
How it is calculated
BMR is what you burn doing nothing at all — keeping a heart beating and a body warm. What you actually need is BMR multiplied by an activity factor, and that figure, TDEE, is the one any calorie target should be built on.
This uses the Mifflin-St Jeor equation. The older Harris-Benedict equation dates from 1919 and tends to overestimate for modern body compositions; comparison studies have generally favoured Mifflin-St Jeor since 1990. That difference is why calculators disagree — and most of them never say which equation they used.
The largest error is the activity setting. People routinely place themselves a level too high. Training three times a week while sitting for the rest of the day is "light", not "moderate". One level is worth 200–300 kcal a day, which is enough on its own to stall progress.
A 500 kcal daily deficit works out to roughly 0.5 kg a week, since a kilogram of fat carries about 7,700 kcal. The rate does not hold indefinitely — BMR falls as weight does — and eating below BMR is not advised.
Frequently asked questions
Why do calculators give different numbers?
They use different equations. Harris-Benedict generally returns a higher figure than Mifflin-St Jeor. If you know your body fat percentage, Katch-McArdle is more accurate still, but it requires a body composition measurement.
Should I eat at my BMR?
No. BMR excludes all activity, so eating at that level leaves you short. Deficits should be taken from TDEE, and eating below BMR is not recommended.
What if I carry a lot of muscle?
The equation cannot separate muscle from fat, so it will read low for you — muscle is metabolically more expensive. Katch-McArdle, which uses body fat percentage, handles this better.
These are statistical estimates with wide individual variation. They do not apply during illness, pregnancy, lactation, or growth, or while taking medication that affects metabolism. Discuss any change in diet with a clinician or dietitian.