Mifflin-St Jeor Equation

BMR Calculator

Basal Metabolic Rate via the Mifflin-St Jeor equation.

Use this free BMR calculator to estimate your basal metabolic rate — the calories your body burns at complete rest. This basal metabolic rate calculator uses the Mifflin-St Jeor equation and supports metric and imperial units.

Sex

Units

Age

yrs

Height

Weight

Basal Metabolic Rate — kcal / day at rest

This is the energy your body uses at complete rest. To estimate your full daily burn including activity, use the TDEE calculator.

This calculator provides estimates based on published formulas and methodologies. Results are for educational and informational purposes only and should not be considered medical advice.

Understanding your result

Your Basal Metabolic Rate is the number of calories your body needs at complete rest to keep vital functions running — breathing, circulation, and cell production.

BMR typically accounts for 60–70% of total daily energy expenditure. It does not include the energy used for movement or digestion.

To estimate the calories you burn across a full day of activity, combine your BMR with an activity multiplier using the TDEE calculator.

Methodology

We use the Mifflin-St Jeor equation, published in 1990 and widely regarded as the most accurate predictive equation for resting energy expenditure in healthy adults.

The equation takes weight in kilograms, height in centimetres, age in years, and a sex-specific constant.

Imperial inputs are converted to metric prior to calculation.

The formula

The Mifflin-St Jeor equation uses weight, height, age and a sex constant.

Men: BMR = 10 × weight(kg) + 6.25 × height(cm) − 5 × age + 5

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

Result is expressed in kilocalories per day (kcal/day).

References

Frequently asked questions

What is the difference between BMR and TDEE?

BMR is the energy your body uses at rest. TDEE (Total Daily Energy Expenditure) is BMR multiplied by an activity factor, representing the calories you burn across a full day including exercise and movement.

Why does VitaCalculator use Mifflin-St Jeor?

The Mifflin-St Jeor equation has been validated as more accurate than the older Harris-Benedict equation for most healthy adults, which is why it is the modern standard.

Does BMR change over time?

Yes. BMR generally decreases with age and falls when you lose weight, since there is less tissue to maintain. Muscle mass raises BMR relative to fat mass.

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