BMR Calculator.
Mifflin-St Jeor, revised Harris-Benedict and Katch-McArdle side by side.
Show the formulas
- Mifflin-St Jeor (female): 10 × — + 6.25 × — − 5 × — − 161
- Revised Harris-Benedict (female): 447.593 + 9.247 × — + 3.098 × — − 4.330 × —
- Katch-McArdle: 370 + 21.6 × lean mass (weight × (1 − body fat % ÷ 100))
Weight in kg, height in cm, age in years. Imperial entries are converted first.
How it works.
Enter age, sex, height and weight
Mifflin-St Jeor and the revised Harris-Benedict equation both use these four inputs. Sex selects which version of each equation applies.
Optionally add body fat percentage
Katch-McArdle uses lean body mass instead of sex, height and age. Add a body fat figure, for example from the body fat calculator, to see it.
Compare the estimates
Mifflin-St Jeor is the default and is shown first, with the other two beside it. Open the formulas to see your numbers plugged into each one.
Treat it as a prediction
Every figure is a regression estimate fitted to a reference group, not a measurement. Measuring resting energy use takes indirect calorimetry.
FAQ.
What is BMR?
Basal metabolic rate is the energy the body uses at complete rest to keep itself running, expressed in kcal per day. Resting energy expenditure is measured under slightly less strict conditions, and the equations here are commonly used to estimate either.
Why is Mifflin-St Jeor the default?
It needs only age, sex, height and weight, and it was derived from resting energy measurements in 498 healthy adults aged 19 to 78 (Mifflin and colleagues, American Journal of Clinical Nutrition, 1990). Men: 10 × weight in kg + 6.25 × height in cm − 5 × age + 5. Women: the same terms − 161.
What is the revised Harris-Benedict equation?
In 1984 Roza and Shizgal re-derived the original Harris-Benedict equations, adding data on further subjects that Benedict had published later (American Journal of Clinical Nutrition). Men: 88.362 + 13.397 × weight + 4.799 × height − 5.677 × age. Women: 447.593 + 9.247 × weight + 3.098 × height − 4.330 × age, in kg, cm and years.
When is Katch-McArdle useful?
It predicts BMR from lean body mass alone: 370 + 21.6 × lean mass in kg. Because it ignores sex, height and age, it is only as good as the body fat figure behind the lean mass, and any body fat estimate carries its own error.
Why don't the three equations agree?
Each was fitted to a different group of people, so each predicts best for people similar to its reference sample. Differences between them are normal and are a reminder that all three are estimates, not measurements.
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