Lean Body Mass Calculator — Boer Formula

Estimate your fat-free mass from height and weight — or exactly, from a measured body-fat percentage.

  • Nutrition
  • 2 cited sources
  • Runs in your browser
Sex
Unit system

Your estimated lean body mass

61.4 kg

Estimated via the Boer formula. That’s 77% of your bodyweight as muscle, bone, organs and water — an estimate, not a scan result.

Methodology

Two routes to lean body mass:

  1. Boer formula (default): men LBM = 0.407W + 0.267H − 19.2; women LBM = 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.
  2. 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

FitTools · sources

  1. 01 Boer P. Estimated lean body mass as an index for normalization of body fluid volumes in humans. Am J Physiol 1984;247:F632–636
  2. 02 Morton RW, et al. Br J Sports Med 2018;52:376–384 (protein for lean-mass gain)

Every formula cited ✓

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 — 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 — the Boer formula was developed in that clinical context.
How do I increase lean body mass?
Progressive resistance training with adequate protein (roughly 1.6–2.2 g/kg/day) is the evidence-backed combination. Gains are gradual — think kilograms per year, not per week.

Written and reviewed by Mathew Beale — MSc Biotechnology, University of Reading.

Last reviewed:

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