Lean body mass calculator
This lean body mass calculator estimates your fat-free body mass (LBM): everything in the body that is not fat – muscle, bone, organs and body water. It works from height and weight or from your body fat percentage.
Example: Units: imperial (ft, in, lb) · Sex: female · Height (feet) 5 ft · Height (inches) 5 in · Weight (pounds) 143 lb → Lean body mass (LBM): 101.7 lb (71.1% of body weight). Source: Boer 1984, Boer P (1984): Estimated lean body mass as an index for normalization of body fluid volumes in humans. Am J Physiol 247(4 Pt 2):F632–F636. Updated: .
How it is calculated
How lean body mass is calculated
Lean body mass (LBM) is body weight without body fat. The calculator uses two published formulas, with weight W in kg and height H in cm:
- Boer (1984): men 0.407 × W + 0.267 × H − 19.2 · women 0.252 × W + 0.473 × H − 48.3
- Hume (1966): men 0.3281 × W + 0.33929 × H − 29.5336 · women 0.29569 × W + 0.41813 × H − 43.2933
If you know your body fat percentage, a simple sum is enough: lean mass = weight × (1 − body fat share). That is more accurate than any formula when the percentage was measured well.
Example: man, 80 kg (176 lb), 180 cm (5 ft 11 in): Boer 0.407 × 80 + 0.267 × 180 − 19.2 = 61.4 kg (77%). Hume 57.8 kg. With a measured 20% body fat: 80 × 0.8 = 64 kg.
How to calculate lean body mass
- Enter sex, height and weight.
- Optionally add your body fat percentage (leave 0 if unknown).
- Read lean mass, fat mass and the comparison of both formulas.
Fat-free mass index (FFMI)
Dividing lean mass by height squared gives the fat-free mass index (FFMI) in kg/m². It makes people of different heights comparable, much like BMI. The calculator deliberately gives no classification.
Limits of the estimate
- The formulas come from samples (Hume measured via body water) and hold only on average.
- With marked overweight, very low body fat or a lot of muscle, errors of several kilograms can occur.
- They are not meant for children, pregnant women or people who are ill.
Related: the body fat calculator estimates your fat percentage, the BMI calculator relates weight to height, and the protein intake calculator gives protein amounts for keeping muscle.
Frequently asked questions
What is lean body mass?
Lean body mass (fat-free mass, LBM) is everything in the body except body fat: muscle, bone, organs, skin and the water in tissue.
How do you calculate lean body mass?
With a known body fat percentage: weight × (1 − fat share). Without it, with formulas such as Boer or Hume from weight, height and sex.
What should my lean body mass be?
There is no fixed target. It depends on height, sex, age and training. Typically lean mass makes up a larger share of body weight in men than in women.
How can I increase lean body mass?
Through strength training with enough energy and protein. The protein intake calculator gives the ranges named in position statements.
How accurate are the formulas?
They are estimates. For a precise value have your body composition measured, for example with DXA or bioimpedance.
Sources and legal basis
- Boer 1984: Boer P (1984): Estimated lean body mass as an index for normalization of body fluid volumes in humans. Am J Physiol 247(4 Pt 2):F632–F636
- Caruso D et al. (2018): Lean Body Weight-Tailored Iodinated Contrast Injection in Obese Patient: Boer versus James Formula. BioMed Res Int 2018:8521893 (reproduction of the Boer formula)
- Hume 1966: Hume R (1966): Prediction of lean body mass from height and weight. J Clin Pathol 19:389–391
- VanItallie TB et al. (1990): Height-normalized indices of the body’s fat-free mass and fat mass. Am J Clin Nutr 52:953–959
As of: · Editorial policy
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