BMR Calculator
Your basal metabolic rate is what your body uses to keep running at complete rest. It is 60–70% of most people's total daily burn.
Your results
BMR equations are population averages. Measured resting metabolic rate varies by roughly 5–10% between people of the same size.
The three equations
Mifflin-St Jeor (1990) is the default and the best-validated for general populations. It uses total body weight.
Katch-McArdle uses lean mass instead: 370 + (21.6 × lean kg). Because it ignores fat mass, it is more accurate for people who are very lean or carrying a lot of fat — but it needs a body-fat figure, and that figure has its own error.
Harris-Benedict dates from 1919, revised in 1984. It tends to read slightly high. Included because it is still widely cited.
What BMR is not
BMR is not what you burn in a day. Add activity — even sedentary activity — and you get total daily energy expenditure, which is 20% to 90% higher. Do not eat at your BMR.
It is also not a measure of how 'fast' your metabolism is in any meaningful sense. The largest determinant of BMR is simply how much of you there is, and most of the variation between people in total daily burn comes from movement rather than resting rate.
Common questions
Which BMR formula is most accurate?
Mifflin-St Jeor for most people. Katch-McArdle if you have a reliable body-fat measurement.
Should I eat at my BMR to lose weight?
No. That is well below your daily expenditure and unnecessarily aggressive. Use TDEE as the reference point instead.
Does muscle raise my BMR a lot?
Less than commonly claimed. Muscle costs roughly 13 kcal per kg per day at rest, so 5 kg of new muscle adds about 65 kcal.
Why does my BMR fall when I lose weight?
A smaller body costs less to run. Expect roughly 20–25 kcal per kg lost, plus a modest adaptive effect.
Related calculators
Track the numbers, not just calculate them
MyFitsy stores your weight, measurements and every session, so the figures above become a trend instead of a one-off.
