Lean Body Mass Calculator
Estimate the weight of everything in your body that isn't fat, muscle, bone, organs and water, using the Boer and Hume formulas.
Estimated lean body mass
- Boer
- 61.5 kg
- Hume
- 57.6 kg
- Implied body fat
- 27.1%
- Fat mass
- 22.1 kg
Worked examples
How LBM is calculated
Lean body mass (LBM) is your total bodyweight minus fat mass. This calculator averages two well-validated equations that estimate LBM from height and weight:
- Boer (1984): Men:
0.407 × kg + 0.267 × cm − 19.2. Women:0.252 × kg + 0.473 × cm − 48.3. - Hume (1966): Men:
0.32810 × kg + 0.33929 × cm − 29.5336. Women:0.29569 × kg + 0.41813 × cm − 43.2933.
Both formulas were originally developed for medical dosing of drugs that distribute through lean tissue. They work well for adults in a normal weight range; they understate LBM for very muscular people and overstate it at very high body fat percentages.
How to use your LBM
LBM is useful in three places:
- Setting protein: some athletes prefer 2.2-2.6 g/kg of LBM rather than total bodyweight (especially at higher body fat).
- Tracking progress: if your weight drops while LBM holds, you've successfully cut fat. If LBM drops too, you're losing muscle.
- Setting a long-term ceiling: natural muscle gain has a known cap. Knowing your current LBM helps set realistic goals.
Worked examples
Example 1. 82 kg man, 178 cm. Boer ≈ 61.5 kg. Hume ≈ 57.7 kg. Average LBM ≈ 59.6 kg. Implied body fat ≈ 27%.
Example 2. 65 kg woman, 165 cm. Boer ≈ 46.1 kg. Hume ≈ 44.9 kg. Average LBM ≈ 45.5 kg. Implied body fat ≈ 30%.
Example 3. 95 kg man, 185 cm. Boer ≈ 69.0 kg. Hume ≈ 64.4 kg. Average LBM ≈ 66.7 kg. Implied body fat ≈ 30%.
Common mistakes
- Treating LBM as muscle. LBM also includes bone, water, organs and connective tissue.
- Using it for very lean athletes. These formulas understate LBM in trained, low-body-fat populations.
- Comparing to a smart scale. Consumer bioimpedance scales swing 3-5 kg between readings; this estimate is steadier.
- Chasing a single LBM number. Trend over months matters more than today's reading.
FAQ
What is lean body mass?+
Everything in your body that isn't fat: muscle, bone, organs, blood, water, skin. LBM is what burns calories at rest and what we try to preserve while dieting.
Is LBM the same as muscle mass?+
No. Muscle is a big chunk of LBM but not all of it. Lab measurements sometimes split out skeletal muscle mass (SMM) separately.
How accurate are these formulas?+
Boer and Hume are within about 5-10% of DEXA results for the average person. Less reliable for very lean athletes or very high body fat percentages.
Why two different formulas?+
Boer (1984) and Hume (1966) use slightly different coefficients derived from different study populations. Averaging them gives a more robust estimate.
How do I increase LBM?+
Progressive resistance training + adequate protein (~1.6-2.2 g/kg) + small calorie surplus. Newer lifters can add 1-2 lb/month of LBM; advanced lifters much less.
Should I aim for higher LBM?+
For most goals, strength, body composition, longevity, yes. Adding lean mass protects metabolism and joint health as you age.
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