BMR Calculator

BMR, or basal metabolic rate, is the number of calories your body burns at complete rest just to keep you alive. It powers your heart, lungs, brain, and the rest of your organs around the clock. For most adults it's the largest slice of daily calorie burn, often 60 to 70% of the total. Everything you do on top, from walking to working out, adds to it.

The common way is the Mifflin-St Jeor equation: 10 × weight in kg + 6.25 × height in cm − 5 × age, then + 5 for men or − 161 for women. This calculator runs that, and also shows the Harris-Benedict and Katch-McArdle results so you'll see all three. You just enter your age, sex, height, and weight, and it does the arithmetic in either unit.

They're close cousins. BMR is measured under strict rest, fasted and lying still, while RMR, resting metabolic rate, is measured under slightly looser conditions and usually reads a little higher. In everyday use the two are often treated as the same, and the formulas here estimate your BMR. For planning calories, the small gap rarely matters.

Mifflin-St Jeor is the current go-to and is usually the most accurate for the general population, which is why it's the headline number here. Harris-Benedict is the older standard and reads a touch higher. Katch-McArdle wins for some people, but only when you know your body fat percentage, since it works from lean mass. Use Mifflin-St Jeor if you aren't sure.

Multiply your BMR by an activity factor, from 1.2 if you're sedentary up to 1.9 if you train hard daily. That gives your total daily energy expenditure, and you'll burn that many calories in a day. The TDEE calculator does this step and shows every activity level, and the calorie calculator turns it into weight-loss and gain targets.

A little, slowly. Building muscle nudges BMR up, since muscle burns more at rest than fat does, and crash dieting can push it down as your body conserves energy. Age, sex, and genetics set most of it, so that's where to focus, on your activity and intake, not on trying to hack your metabolism.

There isn't one normal number, since BMR scales with your body size, age, and sex. Most healthy adults land somewhere between roughly 1,300 and 1,900 calories a day at rest. A smaller or older woman sits near the low end, while a taller, younger, or more muscular man sits near the top. The typical-profiles table above works out a few examples with the Mifflin-St Jeor formula, but the only figure that matters is yours, so enter your own numbers in the calculator.

Use the Mifflin-St Jeor equation with the female constant: 10 × weight in kg + 6.25 × height in cm − 5 × age − 161. For a 30-year-old woman who is 165 cm and 65 kg, that's 650 + 1,031 − 150 − 161, which comes to about 1,370 calories a day. The only change from the men's version is the last term, − 161 instead of + 5. The calculator applies it automatically when you pick Female.