Calorie Intake Calculator

BMR calculator

Your basal metabolic rate is the energy your body uses at complete rest. See it with three formulas side by side.

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What is BMR?

Basal metabolic rate is the number of calories your body would burn if you stayed in bed all day, awake but not moving and not digesting food. It covers breathing, circulation, temperature control, brain activity and cell repair. For most adults it makes up 60 to 70% of total daily calories.

BMR is not how much you should eat. Eating at or below your BMR for long periods is too little for most people. Use it as the base for your TDEE.

BMR formulas

Mifflin-St Jeor (1990)

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 most accurate general-purpose equation in comparison studies, and the one we use by default.

Revised Harris-Benedict (Roza and Shizgal, 1984)

Men: BMR = 88.362 + 13.397 × weight + 4.799 × height − 5.677 × age
Women: BMR = 447.593 + 9.247 × weight + 3.098 × height − 4.330 × age

The classic formula, updated in 1984. It tends to give slightly higher numbers than Mifflin-St Jeor.

Katch-McArdle

BMR = 370 + 21.6 × lean body mass (kg)
Lean body mass = weight × (1 − body fat % ÷ 100)

Ignores age and sex and works from lean mass instead. It is the better choice if you know your body fat percentage reasonably well, particularly for athletes.

What affects your BMR?

  • Body size and muscle. Larger bodies and more muscle mean a higher BMR.
  • Age. BMR falls slowly through adulthood, largely because muscle mass declines.
  • Sex. Men usually have more lean mass, so a higher BMR at the same weight.
  • Genetics, hormones and health. Thyroid conditions and some medicines can change BMR. A doctor can test this if you suspect a problem.

Strength training is the most reliable way to raise BMR over time, because it maintains and builds muscle.

Frequently asked questions

Is BMR the same as RMR?
Close, but not exactly. Resting metabolic rate (RMR) is measured under less strict conditions and is usually slightly higher than BMR. In everyday use the two terms are treated as the same.
Which BMR formula is most accurate?
For most adults, Mifflin-St Jeor. If you know your body fat percentage from a reliable method such as a DEXA scan, Katch-McArdle can be more accurate.
Can I eat my BMR to lose weight?
It is usually better not to. Your BMR is lower than what you burn in a day, and eating that little for long can make it hard to get enough nutrients. Use the calorie intake calculator to set a target instead.

Reviewed and updated 22 October 2026. See how we calculate.