Lean Body Mass Calculator: Boer Formula
Estimate your fat-free mass from height and weight, or exactly, from a measured body-fat percentage.
- 2 cited sources
- Calculates in your browser
Your answer
Appears here as you enter your details. No demo figures — the number is yours, or it is nothing.
Baseline
Know all your numbers
BMI, resting rate, daily burn, eating target, macros, body fat, waist ratios, heart-rate zones and your fitness age: 15 in all. Answer once, see them together, and stop whenever you like.
Get my Baseline →Methodology
Two routes to lean body mass:
- Boer formula (default): men
LBM = 0.407W + 0.267H − 19.2; womenLBM = 0.252W + 0.473H − 48.3(weight kg, height cm). Published in 1984 for normalising physiological measures, it remains the most used height-and-weight LBM estimate. - Direct calculation when you enter a body-fat percentage:
LBM = weight × (1 − body fat ÷ 100), exactly as accurate as the body-fat figure you provide.
Interpreting your result
Lean body mass bundles everything except fat: muscle, bone, organs, water. Two practical uses dominate. First, tracking: if weight falls but LBM holds, you're losing fat rather than muscle, the outcome diets aim for. Second, feeding into lean-mass-based formulas like Katch-McArdle BMR or protein targets set per kilogram of lean mass.
Expect the Boer estimate and the direct calculation to disagree by a few kilograms, Boer assumes an average build for your height and weight, while the direct route reflects your actual composition.
Limitations
- Boer knows nothing about your training history; muscular people are underestimated and sedentary people overestimated.
- LBM includes water, so glycogen and hydration swings move it day to day, compare like-for-like conditions.
- No formula replaces a DEXA scan where precision genuinely matters.
Sources
Pull the receipts, 2 cited sources
Frequently asked questions
- What is lean body mass?
- Lean body mass is everything that isn't fat: muscle, bone, organs and water. It drives most of your resting calorie burn, which is why it appears in equations like Katch-McArdle.
- How accurate is the Boer formula?
- It estimates LBM from height, weight and sex alone, so it reflects the average build for your size. If you know your body-fat percentage from a reliable measurement, the direct calculation (weight × (1 − body fat)) is better, so enter it and this tool switches automatically.
- Why do clinicians care about lean body mass?
- Several drug doses and physiological estimates scale better with lean mass than total weight, and the Boer formula was developed in that clinical context.
- How do I increase lean body mass?
- Progressive resistance training with adequate protein (roughly 1.6 to 2.2 g/kg/day) is the evidence-backed combination. Gains are gradual, so think kilograms per year, not per week.
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