Nutrition calculator
Katch-McArdle calculator
Estimate BMR from lean body mass instead of height and weight — the formula for people who know their body-fat percentage. Free, instant, no sign-up.
Daily calories by activity level
Lean mass moves as you train — the coach re-runs the number instead of holding you to a stale target.
What is the Katch-McArdle formula?
Katch-McArdle estimates basal metabolic rate from lean body mass alone: BMR = 370 + 21.6 × LBM in kilograms. Fat tissue burns very little at rest, so the formula ignores it entirely and asks only how much metabolically active tissue you are carrying. There is no sex term, because lean mass already captures most of that difference.
How this calculator works
If you enter weight and body fat, we take lean mass as weight × (1 − body fat ÷ 100), then run the formula. If you already have a lean-mass number from a DEXA or InBody scan, enter it directly. The daily-calorie figures multiply BMR by the standard activity factors, 1.2 for sedentary through 1.9 for extra active — the same multipliers every TDEE calculator uses.
Katch-McArdle vs Mifflin-St Jeor
Mifflin-St Jeor and Harris-Benedict infer your body composition from height, weight, age, and sex, which works well for people near the population average and drifts for everyone else. Katch-McArdle skips the inference and measures the thing that matters — but it inherits the error in your body-fat estimate, so a tape-measure guess gives you a tape-measure BMR. If you do not have a body-fat number you trust, the standard BMR calculator is the safer starting point.
Using your number
BMR is the floor: what you would burn lying still all day. Pick the activity row that matches your week for a maintenance estimate, then adjust from there — roughly 500 kcal below it for a steady cut, a few hundred above for a lean gain. Recalculate when your composition changes, because that is the whole point of using this formula rather than one keyed to bodyweight.