How to use the lean body mass calculator
- Pick the formula set. The published formulas use one set of coefficients labeled male and another labeled female.
- Choose your units, then enter height and weight.
- Read the Boer estimate in the headline and compare it with the James and Hume estimates in the table of results.
- Use the remaining-mass and lean-share lines to see how the estimate splits your weight, then Copy, Print or export the CSV.
Formula
Boer (male) = 0.407 x weight + 0.267 x height - 19.2
Boer (female) = 0.252 x weight + 0.473 x height - 48.3
James (male) = 1.1 x weight - 128 x (weight / height)^2
James (female) = 1.07 x weight - 148 x (weight / height)^2
Hume (male) = 0.3281 x weight + 0.33929 x height - 29.5336
Hume (female) = 0.29569 x weight + 0.41813 x height - 43.2933
Weight is in kilograms and height in centimeters, and the answer is in kilograms. Remaining mass is weight minus lean mass. If a formula gives a result that is not between zero and your weight, the page explains that the formulas do not suit those measurements.
178 cm and 80 kg, male coefficients
Boer gives 0.407 x 80 + 0.267 x 178 - 19.2 = 60.89 kg of lean mass, which is 76.1% of 80 kg and leaves 19.1 kg that is not counted as lean.
James gives 62.14 kg and Hume gives 57.11 kg for the same measurements. The 5 kg spread between the formulas shows how rough any single figure is.
What lean body mass includes
Lean body mass is body weight minus fat mass. It includes muscle, bone, organs and the water in them. It is not the same as muscle mass, and the formulas here do not separate the parts.
The three equations were fitted to different groups of people, which is why they disagree. Use one formula consistently when you track changes, and treat the difference between formulas as the size of the uncertainty.
Limits of a formula
A formula that uses height and weight cannot tell a muscular person from someone of the same size with more body fat, so it can be well off for athletes, older adults and people with unusual builds. A scan or a trained professional gives a better picture when it matters.
This page is for general information, not medical advice. Related tools are the body fat calculator, the protein intake calculator and the BMI calculator.
Assumptions and limits
- Height is 100 to 250 cm (39 to 98 inches) and weight is 30 to 300 kg (66 to 660 pounds).
- The formula set follows the published male and female coefficients. It is a choice of equation, not a statement about anyone.
- The results are estimates and can differ from a body composition scan by several kilograms.
- No health targets or thresholds are built in, and nothing is stored or uploaded.
Frequently asked questions
What is the Boer formula?
The Boer formula estimates lean body mass from weight and height. With the male coefficients it is 0.407 times weight in kilograms plus 0.267 times height in centimeters, minus 19.2.
Why do the three results differ?
The Boer, James and Hume equations were built from different groups of people with different methods, so they give different answers for the same measurements. The gap between them is a rough sense of the uncertainty.
Is lean body mass the same as muscle mass?
No. Lean body mass is everything except fat, so it also counts bone, organs and body water. Muscle is only one part of it.
Why did the page refuse my measurements?
The formulas can give a lean mass that is zero, negative or equal to or above your total weight for unusual combinations of height and weight. In that case the page tells you so instead of showing a number that cannot be right.