BMR Calculator

What BMR Means

BMR stands for basal metabolic rate. It is the energy your body would use in a day if you did nothing but rest. Even lying still, your body is busy: your heart beats, your lungs work, your brain stays active, and your cells keep repairing themselves and keeping you warm.

For many adults, this resting energy makes up the largest share of what they use in a day. That surprises people, because it means a large part of your energy use has nothing to do with exercise.

How It Is Worked Out

This calculator uses the Mifflin-St Jeor equation, published in 1990 and widely used by nutrition professionals. It takes ten times your weight in kilograms, adds 6.25 times your height in centimetres, and takes off five times your age in years. It then adds 5 for men or takes off 161 for women.

The result is rounded to the nearest 10 kcal. Showing more detail would suggest a precision that an equation like this doesn’t have.

What It Can’t Tell You

The equation only knows four things about you. It doesn’t know how much muscle you have, and muscle uses more energy than fat, even at rest. It also doesn’t take account of illness, medicines, or thyroid problems, all of which can change how much energy your body uses. If you have a thyroid condition, your doctor’s advice and your reports matter far more than this number.

How to Use Your Result

BMR is most useful as a building block, and it isn’t a target for how much to eat. To estimate what you use in a full day, including walking, work, and exercise, try the calorie calculator, which starts from this same figure.

It also helps explain why very low calorie diets are hard to keep up. Eating far below what your body needs at rest is rarely a good idea without medical supervision. If you are trying to change your weight, a nutritionist can help you find an approach that suits your health and your routine.