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Energy calculator

Katch-McArdle Calculator: BMR From Lean Body Mass

Estimate resting calories per day from lean body mass with the Katch-McArdle formula, using your weight and body fat percentage, with the math shown.

No body fat percentage yet? Estimate one from tape measurements with the body fat calculator.

Estimated resting energy

1,781 kcal/day

Resting estimate from 144 lb of lean body mass

Substituted formulaLean body mass = 180 lb × (1 − 20 ÷ 100) = 144 lb370 + 21.6 × 65.32 kg = 1,781 kcal/day

Converted at 1 lb = 0.45359237 kg: 144 lb of lean body mass = 65.32 kg.

The result uses unrounded values. Formula numbers are rounded to two decimals for display.

A resting estimate from lean mass alone. Its accuracy depends on the body fat percentage you enter.

How this Katch-McArdle calculator works

This Katch-McArdle calculator estimates your resting energy, the calories your body uses in a day at rest, from your lean body mass. Enter your weight and your body fat percentage. The result is a resting estimate in kilocalories per day (kcal/day), the unit food labels call calories, with your lean mass and the substituted formula shown under it.

The equation needs only those two numbers. Sex, age, and height are not part of it, so this page does not ask for them.

The Katch-McArdle formula

Resting kcal per day = 370 + 21.6 × lean body mass in kg

Each kilogram of lean mass adds 21.6 kcal a day to a fixed 370. Two people with the same lean mass get the same number, whatever their sex or age. Its accuracy depends on the body fat percentage you enter.

Pounds are converted at 1 lb = 0.45359237 kg before the formula runs, so the formula always works in kilograms. Every step keeps full precision, and only the final result is rounded, to a whole kcal.

Lean body mass from body fat percentage

Lean body mass is your weight minus your fat mass: lean body mass = weight × (1 − body fat % ÷ 100). This page uses the same lean mass calculation as the body fat calculator and the FFMI calculator on this site.

Cunningham’s paper calls this fat-free mass; this page calls it lean body mass. If you do not have a body fat percentage, the body fat calculator estimates one from tape measurements.

The page accepts a body fat percentage from 2 to 70, the same range as the FFMI calculator. EVR found no body fat range in the published summary of the 1991 paper, so this range is a site rule, not a limit from the study.

Katch-McArdle examples

At 80 kg and 20% body fat, lean mass is 80 × 0.80 = 64 kg. The estimate is 370 + 21.6 × 64 = 1,752.4, or about 1,752 kcal/day.

At 180 lb and 15% body fat, lean mass is 153 lb (69.4 kg), and the estimate is about 1,869 kcal/day. At 60 kg and 28%, lean mass is 43.2 kg and the estimate is about 1,303 kcal/day. At 100 kg and 35%, lean mass is 65 kg and the estimate is about 1,774 kcal/day.

The 100 kg example has almost the same lean mass as the 80 kg example, so the two estimates are close, 1,774 and 1,752 kcal/day, even though the weights differ by 20 kg.

Katch-McArdle and the BMR calculator

The BMR calculator uses the Mifflin-St Jeor equation and shows the revised Harris-Benedict equation for comparison. Both use sex, weight, height, and age, and neither uses body fat.

For a 30-year-old man who weighs 180 lb and is 70 inches tall, Mifflin-St Jeor gives about 1,783 kcal/day and revised Harris-Benedict about 1,865. At 20% body fat his lean mass is 144 lb (65.32 kg), and Katch-McArdle gives about 1,781 kcal/day. For a woman with the same weight, height, and age, Mifflin-St Jeor gives about 1,617, while Katch-McArdle stays at 1,781 at the same body fat, because it has no sex term.

These are differences in arithmetic, not a test of which equation is closer to a measured value for any one person.

Where the equation comes from

J.J. Cunningham proposed this equation in 1991 in the American Journal of Clinical Nutrition. His review looked at studies from the previous decade on resting energy expenditure and fat-free mass in adults over a broad range of body weights. He proposed 370 + 21.6 × fat-free mass as a general prediction equation, and in his review it explained 65 to 90% of the variation in resting energy expenditure.

The Katch-McArdle name comes from the exercise physiology textbook by McArdle, Katch, and Katch. The equation itself is Cunningham’s.

Cunningham also published an older, different equation in 1980: 500 + 22 × lean body mass. It is not the Katch-McArdle formula, and it gives higher numbers. For 180 lb at 20% body fat it gives about 1,937 kcal/day, 156 more than this page. Some published sources mix up the two equations.

Cunningham’s paper calls the result resting energy expenditure, not basal metabolic rate. Many calculators call it BMR; this page labels it a resting estimate.

Limits of the estimate

This is an estimate from a prediction equation, not a measurement. It moves with the body fat percentage you enter. At 180 lb, each point of body fat changes lean mass by 1.8 lb (0.82 kg) and the estimate by about 18 kcal/day, so a body fat figure that is 5 points off moves the result by about 88 kcal/day.

The estimate covers rest only. It does not include the energy you use moving or exercising.

Sources

Cunningham JJ. Body composition as a determinant of energy expenditure: a synthetic review and a proposed general prediction equation. Am J Clin Nutr. 1991;54(6):963–969. doi:10.1093/ajcn/54.6.963. PMID 1957828.

The Katch-McArdle name: McArdle WD, Katch FI, Katch VL. Exercise Physiology: Energy, Nutrition, and Human Performance.

The older 1980 equation: Cunningham JJ. A reanalysis of the factors influencing basal metabolic rate in normal adults. Am J Clin Nutr. 1980;33(11):2372–2374. doi:10.1093/ajcn/33.11.2372. PMID 7435418.

EVR checked the 1991 equation against the paper’s published abstract and several later open-access papers that use it. The full text of the paper was not available to EVR.

Sources last checked: 9 October 2026.

Frequently asked questions

What is the Katch-McArdle formula?

Resting kcal per day = 370 + 21.6 × lean body mass in kg. Lean body mass is your weight minus your fat mass. At 80 kg and 20% body fat, lean mass is 64 kg and the estimate is about 1,752 kcal/day.

Who created the Katch-McArdle equation?

J.J. Cunningham published it in 1991 in the American Journal of Clinical Nutrition, as a general prediction equation from fat-free mass. The Katch-McArdle name comes from the exercise physiology textbook by McArdle, Katch, and Katch.

Why does it not ask for sex or age?

The equation has no sex or age term. It uses lean body mass only, so two people with the same lean mass get the same estimate. The BMR calculator’s equations use sex, height, and age instead.

Is the result BMR or resting energy?

Cunningham’s paper calls it resting energy expenditure. Many calculators call it BMR. This page labels it a resting estimate: the calories your body uses at rest, before any movement or exercise.

How does it compare with Mifflin-St Jeor?

For a 30-year-old man at 180 lb and 70 inches, Mifflin-St Jeor gives about 1,783 kcal/day. At 20% body fat, Katch-McArdle gives about 1,781. The two can differ more for other people, because Katch-McArdle uses body fat and Mifflin-St Jeor uses sex, height, and age.

How accurate is a Katch-McArdle estimate?

It is an estimate from a prediction equation, not a measurement, and it depends on the body fat percentage you enter. At 180 lb, a body fat figure that is 5 points off moves the result by about 88 kcal/day.

Is this the same as the Cunningham equation?

Yes, it is Cunningham’s 1991 equation, 370 + 21.6 × lean body mass. Cunningham also published an older, different equation in 1980, 500 + 22 × lean body mass. It gives higher numbers: about 156 kcal/day more at 180 lb and 20% body fat.