# Katch–McArdle BMR Calculator

> Resting energy expenditure from lean body mass (370 + 21.6 × FFM) using your measured body-fat percentage.

Page: https://freecalculator.tech/tools/katch-mcardle-bmr-calculator
Last reviewed: 2026-11-03

## Formula

Fat-free mass FFM = weight × (1 − body fat% ÷ 100). REE (kcal/day) = 370 + 21.6 × FFM (kg), the fat-free-mass equation commonly called Katch–McArdle.

- Source: Cunningham JJ (1991), Am J Clin Nutr 54(6):963–969 — proposed REE = 370 + 21.6 × FFM from a synthetic review.
- Accuracy depends heavily on how body fat was measured.
- Fat-free mass FFM = weight × (1 − body fat% ÷ 100). REE (kcal/day) = 370 + 21.6 × FFM (kg), the fat-free-mass equation commonly called Katch–McArdle.
- Inputs used: Body weight, Measured body-fat percentage.

## Inputs

- Body weight
- Measured body-fat percentage

## Worked example: 80 kg at 20% body fat

FFM 64 kg → 370 + 21.6 × 64 = 1,752.4 kcal/day.
1. FFM = 80 × 0.80 = 64 kg.
2. REE = 370 + 21.6 × 64 = 1,752.4 kcal/day.

## Common questions

### How is this different from Mifflin–St Jeor?

This equation uses lean mass instead of height, age and sex, so it needs a measured body-fat percentage.

### Is this BMR or TDEE?

It estimates resting energy expenditure. Total daily expenditure needs an activity factor, which you choose separately.

### Which body-fat method should I use?

Any you trust — DXA, skinfolds or bioimpedance — but errors in body fat pass straight into the result.

### How do I use the Katch–McArdle BMR Calculator?

Enter the required values for Body weight, Measured body-fat percentage. The calculator applies the formula on this page and shows the main result with any supporting breakdown so you can check the arithmetic.

### What formula does the Katch–McArdle BMR Calculator use?

Fat-free mass FFM = weight × (1 − body fat% ÷ 100). REE (kcal/day) = 370 + 21.6 × FFM (kg), the fat-free-mass equation commonly called Katch–McArdle. The visible formula section above lists the calculation path and the edge cases the page handles, so the result can be checked without relying on the form alone.

### Can the Katch–McArdle BMR Calculator be used for exact decisions?

Use it as a calculation aid, not as a substitute for checking the underlying rule, contract, policy, or professional advice that applies to your situation. When a result depends on local rules, personal details, prices, or dates, enter those values yourself and confirm them before acting.

## Limitations and assumptions

- Population equation; measured metabolic rate can differ substantially.
- Not for clinical nutrition, illness, pregnancy or minors.
- For general fitness education only — not medical advice, diagnosis or a training prescription. Prediction equations are population estimates; speak with a qualified professional before changing exercise or diet, especially with a health condition.
- The result depends on the values you enter for this katch–mcardle bmr calculator; it does not supply missing rates, rules, prices, dates, or assumptions for you.

## Sources

- American Journal of Clinical Nutrition — https://pubmed.ncbi.nlm.nih.gov/1957828/

## Cite this page

- APA: Free Calculator. (2026, November 3). Katch–McArdle BMR Calculator. https://freecalculator.tech/tools/katch-mcardle-bmr-calculator
- MLA: "Katch–McArdle BMR Calculator." Free Calculator, 3 Nov. 2026, https://freecalculator.tech/tools/katch-mcardle-bmr-calculator.
- Link: Katch–McArdle BMR Calculator — Free Calculator, https://freecalculator.tech/tools/katch-mcardle-bmr-calculator