What’s your
BMR?

About the BMR calculator

This calculator estimates your Basal Metabolic Rate — the number of calories your body uses in a day if you did nothing but rest. Even asleep, your organs, brain and muscles need energy, and for most people that resting need is the largest single part of their daily calorie budget. Knowing it is the starting point for any plan to lose, gain or maintain weight.

How to use it

Choose your sex, enter your age, and pick metric or imperial units before typing your height and weight. A 30-year-old man who is 180 cm and 80 kg has a BMR of about 1,780 calories a day. Because the estimate depends on your real measurements, use current figures rather than rounded ones. The table below then multiplies your BMR by common activity levels to show roughly how many calories you would need to maintain your weight.

The formula

This uses the Mifflin-St Jeor equation, $BMR = 10w + 6.25h - 5a + s$, where $w$ is weight in kilograms, $h$ is height in centimetres, $a$ is age in years and $s$ is a constant that is $+5$ for men and $-161$ for women. To get daily needs, multiply the result by an activity factor from about 1.2 for a desk-bound lifestyle up to 1.9 for hard daily training. That product is called your TDEE.

Where it is used

Dietitians and personal trainers use BMR to set calorie targets, and fitness apps use it behind the scenes to build meal and macro plans. It helps explain why two people of the same weight can need very different amounts of food, since age, height and sex all shift the number. As a resting baseline it is also used in clinical settings to estimate energy needs, though individual metabolism can vary by 5–10% from any formula.