BMR Katch-McArdle Calculator
The Katch-McArdle formula calculates Basal Metabolic Rate (BMR) using lean body mass rather than total body weight. This makes it more accurate for people who know their body fat percentage, since muscle tissue burns more calories at rest than fat tissue. The formula is: BMR = 370 + (21.6 x lean body mass in kg). Enter your total weight and body fat percentage and the calculator will derive lean body mass, then compute your BMR in kilocalories per day.
Katch-McArdle formula
Lean Body Mass (kg) = Weight x (1 - Body Fat% / 100)
BMR (kcal/day) = 370 + (21.6 x LBM)
Where LBM is lean body mass in kilograms. The formula was published by Frank Katch and William McArdle in their foundational text on exercise physiology and is widely used in sports nutrition and clinical dietetics.
Activity multipliers for Total Daily Energy Expenditure
- Sedentary (little or no exercise): BMR x 1.2
- Lightly active (1-3 days/week exercise): BMR x 1.375
- Moderately active (3-5 days/week): BMR x 1.55
- Very active (6-7 days/week hard exercise): BMR x 1.725
- Extra active (very hard exercise plus physical job): BMR x 1.9
BMR Katch-McArdle calculator: frequently asked questions
What is the Katch-McArdle BMR formula?
The Katch-McArdle formula calculates BMR using lean body mass (LBM) rather than total body weight. The formula is: BMR = 370 + (21.6 x LBM in kg). It was developed by Frank Katch and William McArdle and published in their textbook Exercise Physiology.
How is lean body mass calculated?
Lean body mass equals total body weight minus fat mass. Fat mass is calculated as body weight multiplied by body fat percentage divided by 100. For example, a 70 kg person with 20% body fat has a fat mass of 14 kg and a lean body mass of 56 kg.
Why is the Katch-McArdle formula more accurate than Harris-Benedict?
The Harris-Benedict formula uses total body weight, height, age, and sex, but does not account for body composition. Two people with the same weight can have very different amounts of muscle and fat. The Katch-McArdle formula uses lean body mass directly, making it more accurate for athletes, bodybuilders, and anyone who knows their body fat percentage.
What units does this calculator use?
This calculator accepts weight in kilograms (kg) and body fat percentage as a number between 0 and 100. The output BMR is in kilocalories per day (kcal/day). To convert pounds to kilograms, divide by 2.2046.
Can I use this BMR to estimate daily calorie needs?
Yes. Multiply your BMR by an activity factor: 1.2 for sedentary (little or no exercise), 1.375 for lightly active (light exercise 1-3 days per week), 1.55 for moderately active (moderate exercise 3-5 days per week), 1.725 for very active (hard exercise 6-7 days per week), and 1.9 for extra active (very hard exercise and physical job). The result is your Total Daily Energy Expenditure (TDEE).
Official sources
- Katch, Frank I., McArdle, William D., Katch, Victor L. (2011). Exercise Physiology: Nutrition, Energy, and Human Performance, 7th edition. Lippincott Williams & Wilkins.
- National Institutes of Health, National Library of Medicine: Resting Metabolic Rate: Best Ways to Measure It and Predict It.
Reviewed by the CalculatorHub team, edited by James Graham, 14 June 2026. See our methodology.