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Katch-McArdle TDEE Calculator (Lean Body Mass)
The Katch-McArdle equation estimates BMR from your lean body mass instead of your total weight, which can make it the most accurate formula — provided you know your body-fat percentage. The formula is BMR = 370 + 21.6 × lean-kg, where lean-kg = weight × (1 − body-fat%), so it ignores age and sex entirely and rewards a leaner, more muscular build with a higher resting burn. This calculator asks for your body-fat % (from a DEXA scan, calipers or a smart scale), computes lean mass, and then multiplies BMR by your activity factor (1.2–1.9) for TDEE, applying your goal for cut, maintain or bulk calories in kcal. If you do not have a reliable body-fat figure, use Mifflin-St Jeor instead — a guessed body-fat % makes Katch-McArdle no better than the alternatives. This is a fitness estimate, not medical or dietary advice.
Katch-McArdle BMR = 370 + 21.6 × lean-kg (lean-kg = weight × (1 − body-fat%))
- Ignores age and sex — driven by lean body mass, so you must enter body-fat %
- TDEE = BMR × activity factor; goal calories = TDEE × (1 + goal%)
Frequently asked questions
When is Katch-McArdle better than Mifflin-St Jeor?
Katch-McArdle can be the most accurate BMR formula when you know your body-fat percentage, because it works from lean mass — the tissue that actually drives resting metabolism. It is especially useful for lean or muscular people, whose BMR the weight-based formulas can understate. Without a reliable body-fat figure, though, use Mifflin-St Jeor instead.
How do I find my body-fat percentage for this?
A DEXA scan is the most accurate, followed by skinfold calipers done consistently; bioimpedance smart scales are convenient but less precise. Any reasonable estimate is fine to start with — just be aware that the accuracy of a Katch-McArdle BMR is only as good as the body-fat % you feed it.