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BMR Calculator – Basal Metabolic Rate and Daily Calories

Calculate your basal metabolic rate — the calories your body burns at complete rest — with the Mifflin-St Jeor, revised Harris-Benedict or Katch-McArdle formula. Then see how many calories you burn in a day at every activity level.

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How to use the BMR calculator

  1. Choose metric or US units.
  2. Select your sex and enter your age, height and weight.
  3. Pick a formula. If you choose Katch-McArdle, enter your body fat percentage.

You’ll see your BMR, the results from both Mifflin-St Jeor and Harris-Benedict for comparison, and a table of your daily calorie needs (TDEE) for each activity level from sedentary to very active.

The three BMR formulas

Mifflin-St Jeor (1990) — the default:

BMR = 10 × kg + 6.25 × cm − 5 × age + 5 (men) or − 161 (women)

Revised Harris-Benedict (Roza and Shizgal, 1984):

Men: 88.362 + 13.397 × kg + 4.799 × cm − 5.677 × age
Women: 447.593 + 9.247 × kg + 3.098 × cm − 4.330 × age

Katch-McArdle, which uses lean body mass instead of height, age and sex:

BMR = 370 + 21.6 × lean body mass (kg)

Worked example

A 30-year-old man, 175 cm, 75 kg:

  • Mifflin-St Jeor: 750 + 1,093.75 − 150 + 5 = 1,699 kcal a day
  • Harris-Benedict: about 1,763 kcal
  • Katch-McArdle at 20% body fat (60 kg lean mass): 370 + 21.6 × 60 = 1,666 kcal

At a moderate activity level (× 1.55), his daily needs are about 2,633 kcal.

Why the formulas give different answers

Each equation was built from a different group of people measured in a lab. Harris-Benedict was first published in 1919 and tends to give slightly higher numbers for today’s population. Mifflin-St Jeor was developed later from a more modern group. None of them can see how much muscle you have, which is why Katch-McArdle, using lean mass, can suit athletes better. Expect any estimate to be within roughly 10% of your true value.

What affects your BMR

  • Body size: bigger bodies use more energy.
  • Muscle mass: muscle is more metabolically active than fat.
  • Age: BMR falls gradually with age, partly from muscle loss.
  • Sex: men usually have more muscle and a higher BMR.
  • Genetics, hormones and health conditions, such as an underactive thyroid.

Using your BMR

Don’t eat below your BMR for long periods without medical advice. To set a daily target for weight loss or gain, use the calorie calculator, then split it into protein, carbs and fat with the macro calculator. For Katch-McArdle, estimate your body fat with the body fat calculator. This is general information, not medical advice — see our disclaimer.

Frequently asked questions

What is BMR?

Basal metabolic rate is the energy your body needs to stay alive at complete rest: breathing, circulating blood, keeping warm and repairing cells. For most people it is 60% to 70% of the calories they burn each day.

What is a normal BMR?

For adults it is often between about 1,200 and 2,000 calories a day, depending mostly on body size, muscle, age and sex. A 30-year-old man who is 175 cm and 75 kg has a BMR of about 1,699 calories by Mifflin-St Jeor.

Which BMR formula is most accurate?

For most healthy adults, Mifflin-St Jeor is the most accurate of the common equations. Katch-McArdle can be better for very lean or muscular people if you know your body fat percentage accurately, because it uses lean body mass.

What is the difference between BMR and TDEE?

BMR is what you burn at rest. TDEE (total daily energy expenditure) adds everything else: walking around, exercise and digesting food. TDEE is the number to use when planning how much to eat.

Can I increase my BMR?

Building muscle raises it a little, because muscle uses more energy than fat even at rest. BMR naturally falls with age and with weight loss.

Is BMR the same as RMR?

They are very close. BMR is measured under strict conditions (after sleep, fasting, at rest); resting metabolic rate (RMR) is measured more loosely and is usually slightly higher. Calculators treat them as the same.

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