What is Katch-McArdle Calculator?
Katch-McArdle is the odd one out among BMR equations: instead of using total body weight, it works from lean body mass, which it multiplies by 21.6 and adds 370. The logic is that fat tissue is metabolically almost inert, so total weight adds noise. If you know your body fat percentage — from a tape measurement, scale or DEXA — this equation can be more accurate than Mifflin-St Jeor, particularly for lean or heavily muscled people for whom weight-based formulas understate or overstate. If you do not know your body fat, estimate it with the Navy tape method first, then enter lean mass here.
Common Uses for Katch-McArdle Calculator
- Get a lean-mass-based BMR if you know your body fat
- Improve accuracy for very muscular or very lean bodies
- Compare against weight-based formulas
Frequently Asked Questions
What is the Katch-McArdle formula?
BMR = 370 + (21.6 × lean body mass in kg). Lean body mass is total weight minus fat mass, which is weight × (1 − body fat % ÷ 100).
When is Katch-McArdle better?
When you know your body fat percentage, especially if you are lean or muscular and the weight-based equations misfit you. Without a body fat measure it is no better than Mifflin-St Jeor.
Why is the constant 370?
It is a fitted intercept representing the metabolic cost of non-fat tissue and regulatory processes, derived from the original regression on lean mass.
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