BMR Calculator

Calculate Basal Metabolic Rate (BMR), resting calorie needs, metabolism, and daily energy requirements.

BMR Calculator

Estimate your basal metabolic rate (BMR), the number of calories your body burns at complete rest to keep essential functions running, such as breathing, circulation, and cell repair. BMR is the foundation for most calorie and nutrition planning.

The Mifflin-St Jeor equation

This calculator uses the Mifflin-St Jeor equation, published in 1990 and recommended by many dietetics organisations because it predicts resting energy needs well across a broad range of adults:

  • Men: BMR = 10 x weight (kg) + 6.25 x height (cm) - 5 x age + 5
  • Women: BMR = 10 x weight (kg) + 6.25 x height (cm) - 5 x age - 161

Weight is in kilograms, height in centimetres, and age in years. Older formulas such as Harris-Benedict are still in use, but Mifflin-St Jeor is generally considered more accurate for modern populations.

BMR itself is not the number of calories you should eat. To estimate total daily needs, BMR is multiplied by an activity factor between about 1.2 (sedentary) and 1.9 (very active); that combined figure is your total daily energy expenditure (TDEE).

Worked example

A 40-year-old man who is 180 cm tall and weighs 80 kg:

  • weight term: 10 x 80 = 800;
  • height term: 6.25 x 180 = 1125;
  • age term: 5 x 40 = 200; and
  • result: 800 + 1125 - 200 + 5 = 1730 kcal per day.

His body burns roughly 1730 kcal per day at rest. A 28-year-old woman who is 160 cm and 55 kg would get 550 + 1000 - 140 - 161 = 1249 kcal per day.

How to interpret your result

BMR from any equation is a screening estimate, not a measurement. True resting metabolism varies between individuals with the same height, weight, age, and sex, mainly because of differences in lean muscle mass, genetics, thyroid function, and medications. Laboratory methods such as indirect calorimetry measure resting energy expenditure directly; a formula can only approximate it, typically within about 10 percent for most adults. Use the number as a baseline for planning and expect to fine-tune based on real-world results.

Practical tips

  • Enter your current weight, not a goal weight, since BMR reflects the body you have now.
  • Never eat at or below your BMR for long periods without professional supervision.
  • Building muscle raises resting metabolism modestly over time; crash dieting can lower it.
  • Recalculate after you gain or lose more than a few kilograms.
  • If your measured results differ a lot from the estimate, trust your own tracked data.

Related calculators

The TDEE calculator converts BMR into total daily calorie needs, and the calories burned calculator estimates the exercise side of the equation. The BMI calculator screens weight relative to height, the heart rate zone calculator helps structure training intensity, and the meal calorie calculator totals the calories in your meals.

This calculator does not replace personalised advice from a qualified healthcare or nutrition professional.

Frequently asked questions

What is basal metabolic rate?
BMR is the number of calories your body uses at complete rest to power essential functions such as breathing, circulation, and cell repair. It typically accounts for 60 to 70 percent of the calories a sedentary person burns in a day.
Which formula does this BMR calculator use?
It uses the Mifflin-St Jeor equation from 1990, which estimates BMR from weight, height, age, and sex. Studies comparing prediction equations have generally found it more accurate for modern adults than the older Harris-Benedict formula, which is why many dietetics organisations recommend it.
Should I eat at my BMR to lose weight?
Generally no. BMR is your resting minimum, not an intake target, and sustainable weight-loss plans usually set calories between BMR and total daily energy expenditure. Eating at or below BMR for long periods creates a very aggressive deficit that is hard to sustain and is best attempted only with professional supervision.
How accurate is a BMR formula?
Prediction equations land within about 10 percent of measured resting metabolism for most adults, but individuals can differ more because of muscle mass, genetics, thyroid function, and medications. Indirect calorimetry in a lab is the only way to measure it directly.
What is the difference between BMR and TDEE?
BMR covers only resting energy use, while TDEE adds everything else: daily movement, exercise, and digestion. TDEE is estimated by multiplying BMR by an activity factor between about 1.2 and 1.9, and it is the number to use when setting calorie targets.
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