Free tool
BMR calculator
Your Basal Metabolic Rate is what you would burn lying still all day — breathing, circulating blood, keeping your organs running. It is the floor your calorie target is built on top of.
What BMR is, and isn’t
BMR accounts for somewhere around 60–70% of what most people burn in a day. It is not a target — eating at your BMR means eating well below what you actually use.
The four numbers underneath are your BMR multiplied by each activity factor. One of them is your real maintenance level, and picking the right one matters more than the BMR figure itself.
This uses the Mifflin–St Jeor equation, which superseded Harris–Benedict as the standard because it is more accurate for modern body compositions.
Want maintenance calories directly? Use the TDEE calculator →
The equation
How BMR is calculated.
Mifflin–St Jeor takes weight, height, age and sex. Every term matters: muscle and organ mass scale with weight and height, and resting metabolism declines with age.
Men carry more lean mass on average at the same height and weight, which is why the constant differs. It is a population average, not a statement about any individual.
| Sex | Formula |
|---|---|
| Men | (10 × weight kg) + (6.25 × height cm) − (5 × age) + 5 |
| Women | (10 × weight kg) + (6.25 × height cm) − (5 × age) − 161 |
Frequently asked questions
Should I eat my BMR to lose weight?
No. BMR is what you burn at rest, so eating at it means a very large deficit once normal daily movement is added. Set your target from TDEE instead, typically 300–500 kcal below it.
Why is my BMR lower than I expected?
BMR scales strongly with body size and lean mass. Shorter, lighter and older people have lower BMRs, and that is normal rather than a sign of a slow metabolism. Actual variation between people of the same size is usually within about 10%.
Does dieting permanently lower my BMR?
BMR falls as you lose weight, mostly because there is less of you to maintain. There is also a modest adaptive component during a deficit that largely recovers when you return to maintenance. Keeping protein high and training helps preserve the lean mass that drives BMR.
Mifflin–St Jeor or Harris–Benedict?
Mifflin–St Jeor. Harris–Benedict dates from 1919 and tends to overestimate for people who are not lean. Katch–McArdle can be better if you know your body fat percentage accurately — you can estimate that with the body fat calculator.
Next step
Knowing the number is the easy half.
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