Basal Metabolic Rate (BMR) is the number of calories your body burns each day to sustain basic life functions — breathing, circulation, and cell production — while at complete rest. It does not include calories burned during activity.

Which BMR formula is most accurate?

The Mifflin-St Jeor equation (1990) is considered the most accurate for most adults and is the preferred formula among registered dietitians. Harris-Benedict (revised 1984) tends to overestimate by about 5%. Katch-McArdle is often the best choice for lean athletes because it accounts for body composition via fat-free mass.

What is the Katch-McArdle formula?

Katch-McArdle calculates BMR from lean body mass (LBM) rather than total weight. Formula: BMR = 370 + 21.6 × LBM(kg), where LBM = weight × (1 − body fat % / 100). It requires a body fat percentage estimate and ignores sex because sex differences are already captured in fat mass.

How do I use BMR to find my daily calorie target?

Multiply your BMR by an activity factor to get TDEE (Total Daily Energy Expenditure): Sedentary ×1.2, Lightly active ×1.375, Moderately active ×1.55, Very active ×1.725, Extremely active ×1.9. Eat below TDEE to lose weight, above to gain.

Does BMR change with age?

Yes. BMR typically decreases with age because of a gradual loss of muscle mass (sarcopenia) and hormonal changes. Maintaining muscle through resistance training can slow this decline.

BMR Calculator

Name: BMR Calculator
Availability: InStock
Author: Nham Vu

Enter your age, sex, height, and weight to instantly calculate your Basal Metabolic Rate (BMR). Add body fat % to unlock the Katch-McArdle formula. All three equations shown side by side.

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Formula

Most accurate for the general population.

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Basal Metabolic Rate

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Basal Metabolic Rate

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kcal / day

Formula: Mifflin-St Jeor

The Mifflin-St Jeor equation uses weight, height, age, and sex. It is the current clinical standard and generally the most accurate for the general population.

Formula Comparison

Formula	BMR (kcal/day)	Notes
Mifflin-St Jeor	—	Clinical standard (1990)
Harris-Benedict	—	Revised 1984; slightly higher
Katch-McArdle	Requires body fat %	Uses lean body mass

BMR is calories burned at rest. Multiply by your activity factor to get TDEE (Total Daily Energy Expenditure). Use the TDEE Calculator for a full breakdown.

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Summary