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Katch-McArdle BMR Calculator (from Body Fat %)

Estimate basal metabolic rate from lean body mass using the Katch-McArdle formula, for anyone who knows their body fat percentage.

Lean body mass
68 kg
BMR (Katch-McArdle, calories/day)
1,839

How it works

The Katch-McArdle formula estimates resting energy expenditure directly from lean body mass, rather than from height, age, and sex the way the Mifflin-St Jeor equation (see the BMR Calculator) does. That makes it a better fit for anyone who already knows their body fat percentage — athletes and bodybuilders in particular, since it credits muscle mass rather than treating two people of the same height, weight, and age but different body composition as having identical metabolisms.

Lean body mass is first found from weight and body fat percentage: LBM = weight × (1 − body fat% ÷ 100). BMR then follows a fixed linear formula: BMR = 370 + 21.6 × LBM (in kilograms). Imperial weight entries are converted to kilograms before the formula runs and the lean body mass result is converted back, so the BMR figure comes out identical either way.

FAQ

How is this different from the site's Mifflin-St Jeor BMR Calculator?

Mifflin-St Jeor estimates BMR from height, weight, age, and sex alone, with no way to account for how muscular someone is. Katch-McArdle instead needs your body fat percentage but, because it works from lean body mass directly, tends to be more accurate for people who are notably more or less muscular than average for their height and weight.

Where do I get my body fat percentage to use here?

This calculator doesn't estimate body fat percentage itself — use a method like the U.S. Navy Body Fat Calculator on this site, a skinfold caliper measurement, a DEXA scan, or a bioelectrical impedance scale, then enter that result here.

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