How this BMR calculator works
Your BMR is the energy your body uses at rest. We estimate it three ways so you can compare.
Mifflin-St Jeor (1990). This is our main result. Weight is in kilograms, height in centimeters, and age in years.
- Men: 10 × weight + 6.25 × height − 5 × age + 5
- Women: 10 × weight + 6.25 × height − 5 × age − 161
A 2005 review found it was the most likely of the common formulas to land within 10% of measured values in healthy adults.
Revised Harris-Benedict (1984). This is an update of the classic Harris-Benedict formula. It uses the same inputs with different numbers. Its authors reported a precision of about 14%.
Katch-McArdle. This one only needs your lean body mass: 370 + 21.6 × lean mass in kg. We work out lean mass from your weight and the body fat percentage you enter. Leave the body fat box blank and this row stays empty.
What your result means
Your BMR is not how much you should eat. It's the floor of what your body uses before you move at all. Your real daily burn, called TDEE, is higher because you walk, work, and exercise. To see that number, use our TDEE calculator.
If the three results are close, you can feel more sure about your estimate. If Katch-McArdle is much higher or lower than the others, check your body fat number. It has a big effect on that formula.
When to use the body fat option
A BMR calculator with body fat can suit people who carry a lot of muscle. Formulas based on total weight can't tell how much of that weight is muscle. Katch-McArdle can, because it starts from your lean mass. If you don't know your body fat, estimate it with our body fat calculator first.
Limits to keep in mind
All three formulas are estimates built from groups of people. Your real number can differ. Some health problems, like thyroid conditions, can change your resting burn. If you have a health condition, talk to your doctor or a registered dietitian before using any formula to plan your diet.
Want the full story on what BMR is and what changes it? Read our guide, what is BMR.