BMR Calculator
The calories your body burns doing nothing at all, from three published equations.
Basal Metabolic Rate is the energy your body uses at complete rest, typically 60 to 70% of the calories you burn in a day. The Mifflin-St Jeor equation estimates it from weight, height, age and sex: 10 x kg + 6.25 x cm - 5 x age, then +5 for men or -161 for women. BMR is not your daily calorie need.
This calculator is for general education only and is not medical advice, diagnosis, or treatment. The equations behind it are population averages: a BMR estimate typically lands within about 10% of a measured resting rate, and further out for some people. Once an activity multiplier is applied, the error on a full-day figure is closer to 20% either side. If you are managing a health condition, are pregnant or breastfeeding, are under 18, or have a history of disordered eating, please work with a doctor or a registered dietitian rather than a calculator.
Your BMR, by Mifflin-St Jeor
The energy your body uses at complete rest. It is not a daily calorie target.
All three equations
These equations disagree by 24 kcal on your numbers, from 1,483 to 1,507. That gap is the honest precision of any single one of them.
If you add your activity level
BMR multiplied by an activity factor is your TDEE, which is the figure to plan intake from.
Whole kcal, rounded once at display. Estimates for adults, roughly 20% either side for an individual. See the notes below.
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About the BMR Calculator
Basal Metabolic Rate is what your body costs to run when you are doing nothing: heart, lungs, kidneys, brain, and the constant work of keeping tissue alive. It is the largest single component of daily energy use for most people, typically 60 to 70% of the total, and it is the number every calorie calculation starts from. This tool shows three published equations at once, because they disagree and that disagreement is worth seeing. Mifflin-St Jeor, published in 1990, is the modern default and generally the most accurate for the general population: the Academy of Nutrition and Dietetics evidence review found it the most likely of the equations to land within 10% of a measured resting rate. The revised Harris-Benedict equation dates from 1984 and tends to read a little higher. Katch-McArdle takes a different approach entirely, estimating from lean body mass, which makes it the most useful of the three if you know your body fat percentage and the least useful if you are guessing at it. Two limits are worth stating plainly. BMR is not your daily calorie target, because you are not in a coma: multiply it by an activity factor to get TDEE, which is the number you would actually eat to. And a strictly measured basal rate requires an overnight fast and rested conditions in a lab, so what these equations give you is an estimate of an estimate. It is genuinely useful as a reference point, and it is not a measurement of your metabolism.
Frequently asked questions
What is the difference between BMR and TDEE?+
BMR is the energy you burn at complete rest. TDEE is everything: BMR plus digestion, plus daily movement, plus exercise. TDEE is BMR multiplied by an activity factor from 1.2 to 1.9, so it is always the larger number and it is the one to use if you are planning what to eat.
What is the Mifflin-St Jeor equation?+
For men, BMR = 10 x weight in kg + 6.25 x height in cm - 5 x age in years + 5. For women, the same but ending in -161. Published in 1990, it replaced Harris-Benedict as the default in most clinical and sports settings because it validated better against measured resting metabolic rates.
Is a low BMR a slow metabolism?+
Usually it just reflects body size. BMR scales with lean mass, so a smaller or lighter person has a lower BMR simply because there is less tissue to run. Genuine metabolic differences between similar people exist but are smaller than most people assume, typically within about 100 to 200 calories at rest. The larger differences between people show up once activity is included, which is TDEE rather than BMR. A result that seems surprisingly low is worth discussing with a doctor rather than acting on alone.
Should I ever eat only my BMR?+
No. Eating at your basal rate means eating nothing for everything else you do that day, which produces a much larger deficit than it looks like. If you are trying to lose weight, take the deficit from your TDEE, and keep intake above the commonly cited minimums of about 1,200 calories for women and 1,500 for men unless a clinician has told you otherwise.
Does BMR change over time?+
Yes. It falls slowly with age, mostly because lean mass declines, and it changes with your weight in both directions. It also drops somewhat during sustained calorie restriction, which is one reason weight loss slows over time and why any long projection from a fixed BMR overstates what will actually happen.
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