BMR Calculator what your body burns

Most of what people repeat about metabolism is folklore. Here is what the measurements say.

It is mostly your organs, not your muscle

At rest, the brain, liver, kidneys and heart do most of the work. Skeletal muscle is large and relatively cheap per kilo. That is why a big weight change moves BMR less than people expect.

It does not slow down at 30

A large study across the human lifespan found resting energy expenditure is stable through adulthood and only starts declining after 60, once the body's lean tissue starts falling. The mid-life weight gain is behaviour and circumstance, not a switch.

Adaptive thermogenesis is real but modest

During a long diet, expenditure falls a little below predictions because you move less and waste less heat. It is worth 100–300 kcal a day for most people — not the thousands the internet claims.

The lever that works

Energy balance. Your BMR sets the floor, activity sets the ceiling, and the difference is what changes weight. For the daily target that follows from these numbers, use the calorie calculator; to see how the result reads against your height, the BMI calculator.