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.

How much does BMR drop when I lose weight?

In the Mifflin-St Jeor equation each kilogram lost lowers BMR by 10 kcal a day, so losing 5 kg cuts it by 50 kcal. BMR also falls by 5 kcal a day for each year of age. Recalculate after a large change in weight.

Can I enter my weight in pounds and height in feet and inches?

Yes. Switch to imperial units and the calculator converts them (1 lb = 0.4536 kg, 1 in = 2.54 cm) before applying the formulas.

BMR Calculator

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.

BMR is the calories your body burns at complete rest.

Your Details

Sex

Male Female

Age (years)

Height

Weight

Body Fat % (optional — enables Katch-McArdle)

Formula

Most accurate for the general population.

Results

Basal Metabolic Rate

Fill in your details and click Calculate.

Age, sex, height, and weight are required.

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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Quick answer

BMR is the calories your body burns at complete rest. The Mifflin-St Jeor equation is 10 × weight (kg) + 6.25 × height (cm) − 5 × age + 5 for men, or − 161 instead of + 5 for women. A 30-year-old man who weighs 80 kg and is 180 cm tall has a BMR of 1,780 kcal a day.

Examples

Person	Mifflin-St Jeor	Harris-Benedict
Man, 30 y, 80 kg, 180 cm	1,780 kcal	1,854 kcal
Woman, 30 y, 65 kg, 165 cm	1,370 kcal	1,430 kcal

Enter your details to compare all three BMR formulas side by side.

Summary

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.

How it works

Select your sex (Male or Female).
Enter your age in years.
Enter your height in cm or switch to feet and inches.
Enter your weight in kg or switch to lb.
Optionally enter your body fat percentage to enable the Katch-McArdle formula.
Choose a formula from the dropdown, then click Calculate.
The right panel shows your BMR and a comparison table for all three formulas.

Use cases

Find out how many calories your body burns at complete rest.
Compare Mifflin-St Jeor, Harris-Benedict, and Katch-McArdle results side by side.
Use BMR as the starting point for calculating TDEE and daily calorie targets.
Understand how body fat percentage affects the Katch-McArdle lean-mass estimate.

Frequently Asked Questions

Last updated: 2026-05-23 · Reviewed by Nham Vu