Katch-McArdle BMR Calculator
The Katch-McArdle formula estimates your basal metabolic rate (BMR) — the calories your body burns at complete rest — from your lean body mass rather than from your total weight, height, and age. Because muscle is more metabolically active than fat, working from fat-free mass makes this formula more accurate than weight-based equations for people who know their body composition, especially lean or athletic individuals. The trade-off is that you need a reliable lean body mass figure, which you can get from a body-composition scan or estimate with our lean body mass calculator. If you do not know your lean mass, the Mifflin-St Jeor BMR calculator, which uses weight, height, and age, is the better starting point.
Calculate
Default result: 1,663
Katch-McArdle BMR Calculator · Result
calculators.dev
Basal metabolic rate
132 lb
This calculator provides general estimates for educational purposes only and is not medical advice. Results are based on population formulas and may not reflect your individual circumstances. Consult a qualified healthcare professional before making changes to your diet, exercise, or health routine.
Reviewed by the calculators.dev team · Last updated 2026-06-23
Formula reviewed against Katch FI, McArdle WD. Nutrition, Weight Control, and Exercise (Katch-McArdle BMR equation from lean body mass)
How to calculate
Enter your lean body mass — your weight minus your fat mass — in pounds or kilograms. The calculator applies the Katch-McArdle equation: 370 plus 21.6 times your lean mass in kilograms. For 60 kg of lean mass that is 370 + 21.6 × 60 = 1666 kcal/day. If you do not have a measured lean mass, estimate it first with the lean body mass or body fat calculator, then return here. To find the calories you burn across a full day, multiply this BMR by an activity factor using the TDEE calculator.
Katch-McArdle: BMR = 370 + 21.6 × LBM_kg, where LBM is lean (fat-free) body mass in kilograms. Variables: LBM is everything in your body that is not fat. The result is kilocalories per day at rest. Because the formula depends only on lean mass, it is more accurate than weight-based equations when body composition is known, but it inherits any error in your lean-mass estimate.
Example calculation
The Katch-McArdle equation is BMR = 370 + 21.6 × lean body mass in kilograms. For someone with 60 kg of lean mass, that is 370 + 21.6 × 60 = 1666 kcal/day. Because it works from lean mass rather than total weight, it adjusts for body composition — two people of the same weight but different muscle will get different results.
- bmr
- 1,666 kcal/day
Assumptions
- The formula needs an accurate lean body mass; an inaccurate lean-mass figure carries straight through to the BMR.
- It is most accurate for lean or athletic people whose body composition is known, and offers little advantage when lean mass is only roughly estimated.
- Like all BMR equations it is a population estimate, not a measured metabolic rate.
Common mistakes
- Entering total body weight instead of lean body mass. The formula expects fat-free mass only — using total weight overstates the result.
- Using a guessed lean mass and treating the BMR as precise. The output is only as good as the lean-mass input.
- Eating only your BMR. BMR is the resting floor; a daily target should be based on TDEE with a moderate deficit.
Frequently asked questions
What is the Katch-McArdle formula?
It estimates basal metabolic rate from lean body mass: BMR = 370 + 21.6 × lean mass in kilograms. Unlike Mifflin-St Jeor, it does not use height or age — it relies on body composition instead, which makes it more accurate for lean, athletic people.
How is Katch-McArdle different from the standard BMR calculator?
The standard BMR calculator uses the Mifflin-St Jeor equation with weight, height, age, and sex. Katch-McArdle uses lean body mass directly. If you know your body composition, Katch-McArdle is often more accurate; if not, use the weight-and-height BMR calculator.
How do I find my lean body mass?
A body-composition scan such as DEXA is most accurate, but you can also estimate it. Use the lean body mass calculator (from weight and height) or the body fat calculator (then subtract fat mass from total weight) and enter the result here.
Should I eat only my BMR calories?
No. BMR is the energy your body uses at rest, before any movement. A sustainable calorie plan is based on your total daily energy expenditure (TDEE) with a moderate deficit. Consult a professional before cutting calories sharply.