BMR Calculator
The calories you burn at rest.
Enter your details to see your result.
What BMR is and why it matters
Your basal metabolic rate is the energy your body uses at complete rest, just to keep you alive. It covers breathing, circulation, body temperature, and the constant background work of your organs. Even if you stayed in bed all day, you would still burn roughly this many calories.
BMR matters because it is the largest single piece of your daily calorie burn, often 60 to 70 percent of the total. Knowing your BMR gives you an honest baseline before you add anything else, which makes it the right place to start if you want to lose, gain, or hold your weight.
The Mifflin-St Jeor equation
This calculator uses the Mifflin-St Jeor equation, widely regarded as the most accurate BMR formula for the general population. It needs only your weight, height, age, and sex.
Men: BMR = 10 × weight(kg) + 6.25 × height(cm) - 5 × age + 5 Women: BMR = 10 × weight(kg) + 6.25 × height(cm) - 5 × age - 161
The only difference between the two lines is the final constant, which accounts for the average difference in body composition between women and men. You enter your numbers above and the calculator does the arithmetic for you.
| Profile | Approx BMR |
|---|---|
| 30yo woman, 165cm, 65kg | ~1,400 kcal |
| 30yo man, 180cm, 80kg | ~1,780 kcal |
| 50yo woman, 165cm, 65kg | ~1,300 kcal |
| 50yo man, 180cm, 90kg | ~1,830 kcal |
BMR vs TDEE
A common mix-up: BMR is not the number you plan meals around. BMR is rest only. Your total daily energy expenditure, or TDEE, is BMR plus everything you do on top of it: walking, training, fidgeting, and even digesting food.
TDEE is always higher than BMR. To get there you multiply BMR by an activity factor. So BMR is the foundation, and TDEE is the figure you actually use for calorie targets. Once you know your BMR here, the next step is to work out your TDEE.
How BMR changes with age and muscle
Two things move your BMR over time: age and muscle mass. As people get older, BMR tends to drop, and a large part of that fall comes from losing muscle rather than age itself.
Muscle is more metabolically active than fat, so a body carrying more muscle burns more calories at rest. That is why two people at the same weight can have different BMRs, and why body composition tells you more than the scale alone. To see where you stand, check your fat-free mass index or estimate your body fat percentage.
Using BMR to plan your calories
Your BMR is the starting point for a calorie plan, not the finish line. Once you have your TDEE, you can set a target: roughly a 10 to 20 percent deficit to lose fat, or a small surplus to build muscle. Crash diets that drop far below your BMR tend to backfire, because they cost you muscle and pull your BMR down with it.
A steadier approach protects muscle and keeps your metabolism working with you. From your calorie target you can split protein, carbs, and fat with the macro calculator to turn the number into a real plan.
Frequently asked questions
What is my BMR?
Your BMR, or basal metabolic rate, is the number of calories your body burns at complete rest just to stay alive: breathing, circulating blood, and keeping your organs running. For most adults it sits somewhere between 1,300 and 1,900 kcal a day. This calculator estimates it from your weight, height, age, and sex using the Mifflin-St Jeor equation.
How do you calculate BMR?
This calculator uses the Mifflin-St Jeor equation, the most accurate formula for the general population. It takes your weight in kilograms, height in centimetres, and age, then adjusts by sex. You enter your numbers above and it returns your basal metabolic rate in calories per day. No body fat measurement is needed for the basic estimate.
What is the difference between BMR and TDEE?
BMR is rest only: the calories you burn doing nothing. TDEE, your total daily energy expenditure, is BMR plus everything else, including walking, exercise, and digesting food. TDEE is always higher than BMR. Use BMR as the foundation, then apply an activity factor to reach the TDEE figure you actually plan calories around.
Does BMR decrease with age?
Yes, BMR tends to fall as you get older, partly because people lose muscle over the years. The Mifflin-St Jeor equation builds this in by subtracting calories for each year of age. The good news is that much of the decline comes from lost muscle, so staying active and preserving muscle keeps your basal metabolic rate higher than it would otherwise be.
Does muscle increase your BMR?
Muscle is more metabolically active than fat, so a body with more muscle burns more calories at rest. This is why two people of the same weight can have different BMRs. It is also why losing muscle during a diet lowers your BMR and makes maintaining weight loss harder. Preserving muscle protects your resting calorie burn.
Is the Mifflin-St Jeor equation accurate?
For most people it is the most reliable BMR formula available without lab testing, and it is the one major dietitian bodies recommend. It is an estimate, not a measurement, so treat the result as a solid starting point. Very lean, very muscular, or very large bodies may need a body composition based formula for a closer figure.
Keep reading
The scale only tells you total weight. Body composition shows whether you are losing fat or muscle, which is what actually matters.
Appetite drops on GLP-1 medications, which makes protein hard to hit. Here is a simple target and practical ways to reach it.