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BMR Calculator

The calories your body burns doing nothing at all.

Inputs
Sex

The equation uses different constants for male and female bodies.

years
kg
cm
Basal metabolic rate
1,649kcal/day
Sedentary (little exercise)
1,979kcal/day
Moderate (3–5 days/week)
2,556kcal/day
Very active (6–7 days/week)
2,844kcal/day
Mifflin-St Jeor: (10 × kg) + (6.25 × cm) − (5 × age) + 5 (male) / − 161 (female)

Activity multipliers are broad averages. Track your actual intake for two weeks to calibrate.

Every tool runs entirely in your browser. Your files are never uploaded to a server.

Basal metabolic rate is the energy your body uses at complete rest to run your heart, brain, lungs and other organs. For most adults it accounts for roughly 60 to 70 percent of daily calorie burn. Enter your details above for an estimate.

How to use the BMR Calculator

  1. Select your sex. The Mifflin-St Jeor equation applies a different constant for male and female bodies.
  2. Enter age, weight and height. Use kilograms and centimetres. Age is in whole years.
  3. Read your rest and activity figures. Your BMR appears first, followed by estimated daily needs at three activity levels.

About basal metabolic rate

Basal metabolic rate describes the energy cost of simply staying alive: maintaining body temperature, circulating blood, breathing, repairing tissue and running the nervous system. Measured properly it requires an overnight fast and a period of complete rest in a controlled environment, so in practice almost everyone uses a predictive equation instead. The Mifflin-St Jeor equation used here was published in 1990 and validated against indirect calorimetry; it is now the formula most dietitians reach for, having largely displaced the Harris-Benedict equation of 1919. Both remain estimates. Individual results vary by around ten percent in either direction because the equations cannot see your body composition, and lean mass is metabolically far more expensive to maintain than fat mass. Two people of identical height, weight, age and sex can therefore have genuinely different basal rates. Thyroid function, recent dieting history, ambient temperature and medication all shift the figure further. Treat the number as a starting point for setting a calorie target, then adjust it against what actually happens to your weight over several weeks.

Frequently asked questions

What is the difference between BMR and TDEE?
BMR is what you burn at complete rest. TDEE is total daily energy expenditure, which is BMR multiplied by an activity factor to include movement, exercise and digestion.
Which BMR equation is most accurate?
Mifflin-St Jeor, used here, is generally more accurate for modern populations than the older Harris-Benedict equation, though both are estimates with roughly ten percent error.
Why does my BMR fall as I lose weight?
A smaller body needs less energy to maintain. BMR drops as weight falls, which is why calorie targets set at the start of a diet stop working partway through.
Is my data sent anywhere?
No. The equation runs in JavaScript in your browser. Nothing you enter is transmitted to us or stored on any server.

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