Calorie Calculator with Body Fat (Katch-McArdle)
If you know your body-fat percentage, the Katch-McArdle formula gives a sharper calorie estimate by basing your metabolism on lean mass — the tissue that actually burns energy.
Your details
Lean mass vs fat mass
Katch-McArdle bases your BMR on lean mass — muscle, organs, and bone.
How your target is built
Standard calorie formulas use only your weight, height, age, and sex. The Katch-McArdle equation goes further: it calculates your BMR from your lean body mass, which makes it more accurate for lean, muscular, or athletic people whose body composition differs from average. Enter your body-fat percentage and the calculator separates your weight into fat and lean mass, then builds your calorie target from there.
How the Katch-McArdle formula works
Katch-McArdle estimates BMR as 370 + 21.6 × lean body mass (in kilograms), where lean mass is your total weight minus your fat mass. Because muscle and organs burn far more energy at rest than fat does, tying BMR to lean mass captures your true metabolism better than weight alone — especially if you carry more or less muscle than the average person.
The donut on this page splits your weight into lean and fat mass so you can see the two components the formula relies on. From your BMR we apply your activity factor for TDEE, then adjust for your goal.
When to use Katch-McArdle vs Mifflin–St Jeor
If you know your body-fat percentage with reasonable accuracy — from a DEXA scan, calipers, or a smart scale — Katch-McArdle is the better choice, particularly for athletes and very lean or very muscular individuals. If you don't know your body fat, the Mifflin–St Jeor equation used by our main calorie calculator is the more practical option.
Whichever formula you use, the result is an estimate. Track your weight over a few weeks and adjust your intake based on what actually happens on the scale.
Frequently Asked Questions
Katch-McArdle estimates your BMR from lean body mass: BMR = 370 + 21.6 × lean mass in kilograms, where lean mass is your weight minus your fat mass. It's more accurate for people who know their body-fat percentage.
It can be, for lean and muscular people, because it accounts for body composition rather than assuming an average. But it requires knowing your body-fat percentage. Without that, Mifflin–St Jeor is the practical choice.
Options range from a DEXA scan (most accurate) to skinfold calipers, bioelectrical-impedance smart scales, or visual estimation charts. Even a rough figure improves the Katch-McArdle estimate over weight alone.
Lean body mass is everything in your body that isn't fat — muscle, bone, organs, and water. Since it's the metabolically active tissue, Katch-McArdle uses it to estimate how many calories you burn at rest.
Yes. Even with the Katch-McArdle method, your target won't drop below 1,200 calories for women or 1,500 for men, and you'll see a note if it's raised to that floor.
These results are estimates for general educational purposes only and are not medical or nutritional advice. Individual needs vary. Consult a qualified healthcare professional or registered dietitian before making significant changes to your diet, especially if you are pregnant, breastfeeding, under 18, or have a medical condition.