How to use the Lean Body Mass Calculator
- Choose your sex and the unit system.
- Enter your height and weight.
- Read the lean body mass from each formula and the average.
- Use the fat mass and body fat figure as a rough guide only.
Formula used
Boer: men 0.407w + 0.267h − 19.2, women 0.252w + 0.473h − 48.3. James: men 1.1w − 128(w ÷ h)², women 1.07w − 148(w ÷ h)². Hume: men 0.3281w + 0.33929h − 29.5336, women 0.29569w + 0.41813h − 43.2933. Weight w in kg and height h in cm.
Worked example
Here is the Lean Body Mass Calculator worked through with the example values shown above, so you can check each step by hand.
| Inputs | |
|---|---|
| Sex | Male |
| Units | Metric (cm, kg) |
| Height (cm or inches) | 175 |
| Weight (kg or pounds) | 75 |
| Result | |
| Lean body mass, average of formulas (kg) | 57.163149 |
| Lean body mass (pounds) | 126.02317 |
| Fat mass (kg) | 17.836851 |
| Estimated body fat | 23.78% |
| Boer (kg) | 58.05 |
| James (kg) | 58.989796 |
| Hume (kg) | 54.44965 |
The three formulas
The Boer, James and Hume formulas each predict lean mass from weight and height. For a man of 175 cm and 75 kg they give 58.1 kg (Boer), 59 kg (James) and 54.4 kg (Hume). The average is 57.2 kg, or 126 lb.
Fat mass is weight minus lean mass, 17.8 kg here, which makes an estimated body fat of 23.8%. For a woman of 165 cm and 62 kg the average lean mass is 44.9 kg and the body fat estimate 27.5%.
How accurate is it
These formulas use only height and weight, so they cannot see how much of your weight is muscle or fat. Two people of the same size can differ by many kilograms of lean mass. The estimates are most useful as a ballpark and for tracking, and less so as a diagnosis.
Methods such as DEXA scans, bioelectrical impedance and skinfold measurements are more direct, though each has its own error.
US units
The calculator converts inches and pounds for you. A 69 inch, 165 lb man works out to about 57.2 kg (126.1 lb) of lean mass.
The formulas were developed for adults with typical builds. They are less suitable for children, very muscular athletes, pregnant women and people with very high or low body weight, so the tool limits the inputs to a range of 100 to 250 cm and 30 to 300 kg.
Using the result
Lean mass helps set protein goals, since needs are often given per kilogram of lean mass or body weight. The protein intake calculator on this site uses body weight. It also feeds metabolic estimates: more lean mass generally means a higher resting energy use.
For health decisions, use the result together with other measures such as BMI, waist-to-hip ratio and advice from a doctor or dietitian.
Frequently asked questions
What is lean body mass?
Your body weight minus body fat: muscle, bone, organs, blood and water.
Which formula is best?
None is clearly best. They differ by a few kilograms, so the calculator shows all three and their average.
Is the body fat estimate accurate?
It is a rough guide. Measurements such as DEXA or skinfolds are more reliable.
Can I use pounds and inches?
Yes. Choose US units and enter inches and pounds.
Why is there a limit on height and weight?
The formulas were designed for typical adult ranges and give poor results outside them.
Does it work for children?
No. These formulas are for adults.
This calculator gives estimates for information only. Actual figures from a bank, employer, tax authority or doctor may differ. It is not financial, tax, legal or medical advice.