About the Lean Body Mass Calculator
Lean body mass (LBM) is everything in your body that is not fat — muscle, bone, organs, skin and water. This calculator estimates it from just your height, weight and sex using three published formulas: Boer (1984), James (1976) and Hume (1966). You can enter pounds with feet and inches or kilograms with centimetres.
Knowing your lean mass helps with setting protein targets (often quoted per kilogram of lean mass), using the Katch-McArdle BMR equation, and judging whether weight changes are coming from fat or muscle. Clinicians also use LBM-based formulas to dose some anaesthetic and chemotherapy drugs.
Height-and-weight formulas assume an average body composition for your size, so they cannot tell a muscular athlete from a sedentary person of the same build. If you have a tape measure, the body fat calculator gives a more personal estimate; DEXA scans are the most accurate option.
With the default inputs, the lean body mass (boer) is 135.6. Change any value above to recalculate instantly.
How to use the lean body mass calculator
- 1Select your sex.
- 2Choose US or metric units.
- 3Enter your height and weight.
- 4Read your lean body mass from the Boer formula and compare the others.
- 5Use the implied body fat and fat mass as a rough composition check.
Formula and method
All three formulas take weight W in kilograms and height H in centimetres. Boer and Hume are linear regressions fitted to measured body composition; James includes a squared weight-to-height term, which makes it curve downward and underestimate lean mass for people with a high BMI. Boer is generally considered the most reliable of the three for adults of typical build and is used as the headline result.
Implied body fat is 1 − LBM ÷ weight. Results are shown in pounds for US units (1 kg = 2.2046 lb) and are capped between zero and total body weight.
- W
- Body weight in kilograms
- H
- Height in centimetres
- LBM
- Lean body mass (fat-free mass)
Worked examples
Man, 5 ft 10 in, 180 lb
In metric he weighs 81.65 kg at 177.8 cm. Boer: 0.407 × 81.65 + 0.267 × 177.8 − 19.2 ≈ 61.5 kg, or about 135.6 lb of lean mass — implying roughly 24.7% body fat. James gives 138.5 lb and Hume 126.9 lb.
Woman, 163 cm, 62 kg (metric)
Boer for women: 0.252 × 62 + 0.473 × 163 − 48.3 = 44.4 kg of lean mass, leaving about 17.6 kg of fat (28%). James gives 44.9 kg and Hume 43.2 kg.
Frequently asked questions
What is a normal lean body mass?+
Lean mass is usually around 75–90% of body weight in men and 65–80% in women, depending on fitness. Because it scales with height and frame size, comparing your own LBM over time is more useful than comparing with other people.
Is lean body mass the same as muscle mass?+
No. Lean body mass includes muscle plus bones, organs, skin, blood and water. Skeletal muscle is typically around half of lean mass, so LBM is always noticeably higher than muscle mass alone.
Which lean body mass formula should I use?+
Boer is generally the best of the height-and-weight formulas for typical adults. James becomes unreliable at high BMI. If you know your body fat percentage from a scan or tape measure, lean mass = weight × (1 − body fat %) is more accurate than any of these.
How can I increase lean body mass?+
Progressive resistance training combined with enough protein (commonly 1.6–2.2 g per kg of body weight per day for people trying to build muscle) and sufficient total calories is the most reliable way to gain lean mass.
This tool gives general estimates and is not medical advice. Talk to a doctor or qualified professional about your health, diet or training.