Lean Body Mass Calculator guide
Lean Body Mass Calculator: Boer, James and Hume Formulas
Use our lean body mass calculator to estimate your lean body mass from your height, weight and sex with the Boer, James and Hume formulas.
By the AllCalculator editorial teamUpdated 16 October 20262 min read
Your lean body mass (LBM) is everything in your body except fat: muscle, bone, organs, skin and water. Our Lean Body Mass Calculator estimates it from your height and weight.
How to use the calculator (Lean Body Mass Calculator)
- Choose your sex.
- Enter your weight and height.
You'll see your lean body mass using three formulas and the body fat each one implies.
The formulas
All three use weight in kilograms and height in centimetres.
- Boer (1984): men 0.407W + 0.267H − 19.2; women 0.252W + 0.473H − 48.3
- James (1976): men 1.1W − 128(W/H)²; women 1.07W − 148(W/H)²
- Hume (1966): men 0.3281W + 0.33929H − 29.5336; women 0.29569W + 0.41813H − 43.2933
The Boer formula is often considered the most accurate for adults of normal weight. The James formula gives odd results at high BMIs.
A worked example
With the calculator's default settings, a woman who is 168cm tall and weighs 70kg has a lean body mass of about 48.8kg using the Boer formula. That's about 70% of her weight, implying around 30% body fat.
What it's used for
- Medicine: some drugs, including anaesthetics, are dosed by lean body mass.
- Fitness: tracking lean mass shows whether you're losing fat or muscle as you lose weight.
- Nutrition: protein targets and the Katch-McArdle BMR formula use lean mass.
Frequently asked questions
How accurate are these formulas?
They're estimates for the average person. They can't tell how muscular you are, so athletes will often have more lean mass than the formulas suggest.
How can I get a better estimate?
Measuring your body fat gives a more personal result. Try our Body Fat Calculator, which uses tape measurements. DEXA scans are the most accurate.
Does lean mass fall with age?
Yes. Adults slowly lose muscle with age, but strength exercises at least twice a week can help keep it.
To see how your lean mass affects your calorie needs, try our BMR Calculator.
Sources and further reading
Links open official and independent websites in a new tab.
This guide is general information to help you understand your options. It isn't financial, tax, legal or building advice and doesn't take your personal circumstances into account. Figures were checked when the guide was last updated and can change, so confirm anything important with GOV.UK, HMRC, a regulated adviser or a qualified tradesperson.