Lean Body Mass Calculator
Work out how much of your weight is lean tissue and how much is fat, using four published anthropometric equations and your own body-fat percentage. See the composition as a stacked bar and watch how the answer moves across the formulas.
Lean body mass (formula average)
48.2kg
18.0% body fat · Average
Reference bands
5%Athletic
13%Fitness
18%Average
24%Above average
32%
- Body mass index
- 23.7
- Formula range
- 18.8 – 59.8 kg
- Healthy lean window
- 56.3 – 69.0 kg
Healthy lean window = your weight at 8% and 25% body fat for a male. ACE 'fitness' band is roughly 14–17%; the health-risk threshold sits near 25%.
Formula spread
Same person, four equations. Bars are lean mass; the marker shows the average and the shaded band is the healthy lean window.
The four equations and their sources
Boer
LBM = 0.407w + 0.267h − 19.2 (male) | 0.252w + 0.473h − 48.3 (female)
Boer, P. (1984), Am J Physiol — from the Hume & Weyers data set
James
LBM = 1.1w − 128(w/h)² (male) | 1.07w − 148(w/h)² (female)
James, W. P. T. (1976), Clin Sci Mol Med — h in cm, w in kg
Hume
LBM = 0.32810w + 0.33929h − 29.5336 (male) | 0.29569w + 0.41813h − 43.2933 (female)
Hume, R. (1966), J Clin Pathol — h in cm
Peters
LBM = 7.38 x 10⁻⁵ x h^1.81 x w^0.646 (male) | 6.37 x 10⁻⁵ x h^1.71 x w^0.61 (female)
Peters, A. et al. (2011), Nutr Clin Pract (paediatric cohort)
How body fat moves the answer
Your weight is fixed, so lean and fat mass trade off exactly. The marker is where you are now.
If you were 5 points leaner
65.3 kg lean · 9.8 kg fat
at 13.0% body fat
Your current estimate
61.5 kg lean · 13.5 kg fat
at 18.0% body fat
If you were 5 points heavier
57.8 kg lean · 17.3 kg fat
at 23.0% body fat
These equations are population averages: they read individual lean mass to within roughly ±3–5 kg and assume an average frame and muscle mass. This is an estimate for general information, not medical advice — DEXA or a displacement scan is the way to measure body composition properly.
About this tool
Lean body mass is everything that is not fat: muscle, bone, organs and water. The calculator applies the Boer, James, Hume and Peters equations to your height, weight and sex, then layers your own body-fat percentage on top so you can compare the two views of the same body. Everything is computed locally in your browser and no measurement leaves the page.
- 100% free — no account needed
- Runs in your browser
- Nothing is uploaded
Frequently asked questions
Is Lean Body Mass Calculator really free?
Yes. Lean Body Mass Calculator is completely free on PureBrowser — every feature, with no account, no trial, and no credit card.
Does Lean Body Mass Calculator upload my data?
No. Lean Body Mass Calculator runs entirely inside your browser, so anything you type, paste, or open stays on your own device.
Do I need to sign up or install anything?
Neither. There is no account and nothing to download — open the page and Lean Body Mass Calculator is ready to use on desktop or mobile.
Does Lean Body Mass Calculator work offline?
Once the page has loaded, yes. All of the processing happens locally in your browser, so it keeps working without a connection.
More health & fitness
BMI Calculator
Calculate your Body Mass Index using metric or imperial units with category breakdown.
Sleep Calculator
Find the best bedtime or wake-up time based on 90-minute sleep cycles. Wake up refreshed with this free sleep cycle calculator.
TDEE Calculator
Calculate your Total Daily Energy Expenditure using the Mifflin-St Jeor formula. Find calorie targets for weight loss, maintenance, or muscle gain.
Ideal Weight Calculator
Calculate your ideal body weight using four clinical formulas: Devine, Robinson, Miller, and Hamwi. Supports metric and imperial units.
Heart Rate Zone Calculator
Find your 5 heart rate training zones based on age or max heart rate. Includes the Karvonen formula with fat burn, aerobic, and VO₂ max zones.
Body Fat Calculator
Estimate body fat percentage using the US Navy circumference method. Enter height, neck, waist, and hip measurements to see your body fat category. Metric and imperial supported.