Katch–McArdle Calculator | Lean-Mass Equation Illustration

Katch–McArdle illustration: REE = 370 + 21.6 × lean body mass in kg. Joseph et al. (July–August 2017), equations section documents this expression. This is a bounded published illustration, not a claim that the original derivation or general validation has been established.

Lean body mass here means the entered non-fat portion of body mass, not muscle mass alone. The calculator does not independently measure it.

1. Choose weight plus body-fat percentage, or direct lean body mass.
2. Select kg or lb. Pounds are converted with × 0.45359237.
3. For the weight method, enter positive weight and body fat from 0 to 100%. For direct lean mass, enter a positive value.
4. Submit to display a rounded equation value in kcal/day.

No age, height, sex or activity input contributes to this formula. Missing composition information is not automatically estimated.

Lean mass (kg) = weight (kg) × (1 − body fat / 100).

For 70 kg with 20% body fat: lean mass = 70 × 0.8 = 56 kg. The equation gives 370 + 21.6 × 56 = 1,579.6 kcal/day, displayed as 1,580 kcal/day. Entering 56 kg directly produces the same value.

This is a reproducible arithmetic example, not proof of that person’s measured expenditure or minimum food needs.

Katch uses lean mass, while Harris–Benedict and Mifflin–St Jeor use total weight, height, age and separate coefficient sets. Fewer inputs make the expression simpler to reproduce; they do not prove greater accuracy.

The linked 2017 study does not support universal athlete superiority. Its tested equations underestimated measured resting energy in the studied weightlifters.

Compare direct lean-mass entry with the equivalent weight/body-fat calculation, or check how units affect the operands. With lean mass held constant, each additional kg changes the equation by 21.6 kcal/day.

No activity multiplier or dietary prescription is calculated here. Any separately chosen multiplication would be an arithmetic scenario, not a verified daily-energy need.

Equation output is predicted resting energy, not measured metabolism or a food-intake target. No automatic deficit, surplus, macronutrient prescription, weekly weight forecast, or medical metabolism grade is inferred.

A study population describes the evidence behind an equation. It does not establish suitability for every person with the same age or measurements, or for illness, pregnancy, lactation, or childhood. Individual nutrition decisions require information beyond these inputs.

Body-fat input uncertainty changes derived lean mass and therefore the output. The accepted percentage interval is a mathematical input bound, not a clinical body-fat recommendation. The 2017 study is narrow evidence; this form is not an independently validated general personal estimator.

Publication: Joseph et al., July–August 2017, DOI 10.4103/ijem.IJEM_563_16. The study involved 30 professional male Asian-Indian weightlifters; all tested equations underestimated measured resting energy in that cohort. It does not establish universal superiority for athletes or the general population.

The cited textbook derivation was not independently reviewed. The 2017 date identifies this paper, not the original formula date. Sources checked on 2026-09-30.

NIST Handbook 44 (2026), Appendix C: 1 lb = 0.45359237 kg; 1 in = 2.54 cm.