BMR Calculator: How Many Calories Your Body Burns at Rest

A BMR calculator estimates how many calories your body burns in a day at complete rest. Enter your sex, age, height, weight and activity level below. You get two numbers: your BMR, and your TDEE, the calories you burn on a typical day including your activity. Both are estimates and a starting point, not an exact measurement.

BMR and TDEE calculator

This calculator needs JavaScript. The formulas are explained below.

What is BMR?

BMR stands for basal metabolic rate: the number of calories your body needs to keep all its basic processes running while you rest. That includes breathing, blood flow, keeping your body temperature steady and building new cells.

You can estimate your BMR with a formula. A formula is never accurate to the last calorie, but it gives a good enough estimate of how much energy your body needs.

How to fill in the calculator

• Sex: the formula is different for men and women.
• Age: your age in years. The formulas were built for adults, so the calculator accepts ages 18 to 100.
• Height: in centimeters (for example 176 cm) or in feet and inches.
• Weight: in kilograms or pounds.
• Activity: how active you are in a typical week, including your job.
• Results: after you press the button, you see your BMR and your TDEE.

The formulas behind the calculator

The calculator shows two common formulas. The main result uses the Mifflin-St Jeor equation (Mifflin and colleagues, 1990):

• Men: BMR = (10 × weight in kg) + (6.25 × height in cm) − (5 × age in years) + 5
• Women: BMR = (10 × weight in kg) + (6.25 × height in cm) − (5 × age in years) − 161

A systematic review of the common formulas found that Mifflin-St Jeor estimated resting metabolic rate within 10% of the measured value in more people than the other equations it tested, including Harris-Benedict.

The second result uses the revised Harris-Benedict equation (Roza and Shizgal, 1984), a formula that many online calculators still use:

• Men: BMR = 88.36 + (13.4 × weight in kg) + (4.8 × height in cm) − (5.7 × age in years)
• Women: BMR = 447.6 + (9.2 × weight in kg) + (3.1 × height in cm) − (4.3 × age in years)

Roza and Shizgal reported that this equation predicts resting energy use in healthy, well-nourished adults with a precision of about ±14%. The two results are usually close. If they differ, you can start from the middle.

How BMR helps you build muscle or lose fat

Your BMR on its own is only part of the picture. To know how much energy you use in a day, you add your work and your exercise. The final number is your starting point for a nutrition plan, whether your goal is to lose fat or to build muscle.

Adding your activity: TDEE

After you know your BMR, you add the calories you burn at work and in your workouts. This total is called TDEE, total daily energy expenditure. To get it, the calculator multiplies your BMR by one of these numbers:

These activity factors are common rules of thumb, not results of the studies listed below, and they are the least precise part of the estimate.

You need to estimate your own activity level here. For example, if your BMR is 1,500 calories and you are moderately active:

• 1,500 × 1.55 = 2,325 calories

That means about 2,325 calories a day is an estimate of what may keep your weight steady. Use it as a starting point for your menu, then adjust by your results.

My tip: estimate, track and adjust

Not sure which activity level fits you? Don't worry. Pick the one that looks closest; you can correct it later. Then track what you eat for a few weeks and watch your weight. If your weight is not moving the way you planned, adjust your daily intake a little and check again.

That is the right way to work: try, check and adjust. A calculator gives you the first number; your own results give you the real one.

What is the difference between BMR and RMR?

RMR is resting metabolic rate. The two terms are close, and many fitness and nutrition professionals use "resting metabolic rate" for both.

The difference is how strictly they are measured. BMR is measured under strict conditions: right after waking, after an overnight fast, lying still in a comfortable room. RMR is also measured at rest, but with looser conditions, so it is usually a little higher than BMR. The gap is small, and the formulas on this page estimate resting energy use.

The limits of a BMR calculator

The number a BMR calculator gives you is not exact, because every body is different. A formula cannot take into account things like:

• Genetics: inherited traits affect your BMR.
• Your own metabolism: two people with the same height, weight and age can burn a different number of calories.
• Muscle mass: people with more muscle burn more calories at rest.
• Pregnancy and breastfeeding: energy needs change, so the calculator is not meant for this time. Ask your doctor or a registered dietitian.
• Age and background: the review above found that older adults and some ethnic groups were underrepresented in the studies behind these formulas, so the error can be larger.

Bottom line

Many people ask themselves why they are not making progress, even after years of training and trying to eat well. Often the answer starts right here: with understanding what your body really needs. BMR and TDEE give you a direction and a good starting point based on your own measurements instead of a guess. From there, the results depend on doing the process well, whether you are losing fat or building muscle.

Frequently asked questions

Is BMR the same as the calories I burn in a day?

No. BMR is only what you burn at complete rest. The calories you burn in a day are your TDEE, which adds your daily activity and exercise.

Which formula is more accurate, Harris-Benedict or Mifflin-St Jeor?

Mifflin-St Jeor, in the review described above, which is why it is the main result. Both are estimates, so adjust by your results.

Should I eat less than my BMR to lose weight?

Most people do not need to eat below their BMR. A common approach is to eat somewhat below your TDEE and adjust by your results. If you have a health condition, or want a plan for large weight changes, talk to your doctor or a registered dietitian.

Does muscle raise my BMR?

Yes. Muscle tissue uses more energy at rest than fat tissue, so more muscle raises your BMR a little.