Health & Fitness
Lean Body Mass Calculator
Lean Body Mass — it estimates lean body mass with the Boer formula from your weight, height and sex, then derives fat mass as body weight minus lean mass. This page runs that same calculation on your numbers, in your browser: no signup, no uploads, nothing stored.
Use Lean Body Mass Calculator to estimate your lean body mass: give it your weight, height and sex, press Calculate, and read off your lean mass and body-fat estimate — all worked out on your device.
About this calculator
It estimates lean body mass with the Boer formula from your weight, height and sex, then derives fat mass as body weight minus lean mass. It matters when you want a quick screening number before deciding whether a habit, plan or measurement deserves a closer look. Here is the calculation on real numbers: For an 80 kg male at 18% body fat: lean mass = 80 × (1 − 0.18) = 65.6 kg . For your own figures, use the calculator above — same method, your inputs, computed on-device.
How to use
- Enter your current body weight in kilograms.
- Provide your height in centimetres for the Boer formula.
- Select your sex for the correct Boer coefficients.
- Press Calculate to see your estimated lean body mass.
Why use Lean Body Mass Calculator
Fast
Calculations run in your browser. No round trip to a server.
Private
Your inputs never leave your device. Nothing is uploaded.
Free
No signup, no paywall, no ads-in-results, no watermarks.
Educational
Uses common estimation formulas for educational purposes. Results are not medical advice and should not replace professional guidance.
Mobile-ready
Optimised for phones, tablets, and desktops alike.
Transparent
Clear about formulas used and their limits, with disclaimers where they matter.
Common uses
Use it for setting realistic training goals
Use it when adjusting diet and exercise
Lean Body Mass alongside a workout plan
Lean Body Mass in personal-training sessions
Use it when tracking progress over time
Use it for comparing before-and-after
Technical notes
Lean Body Mass Calculator estimates lean body mass with the Boer formula from your weight, height and sex, then derives fat mass as body weight minus lean mass.
These are general-population estimates and not a substitute for advice from a qualified clinician.
The tool works offline once loaded, since every computation is client-side.
FAQ
What is lean body mass?
Lean body mass is your total weight minus fat mass — it includes muscle, bone, organs, and body water. It is often used to scale nutrition and medication.
Which formula does this use?
It uses the Boer formula, a widely cited equation that estimates lean mass from weight, height, and sex without needing body-fat measurement.
How is lean mass different from body fat percentage?
Body fat percentage tells you the fat share of your weight; lean mass tells you the absolute weight of non-fat tissue. They are complementary numbers.
Does the Lean Body Mass Calculator send my data to a server?
No. The Lean Body Mass Calculator runs entirely in your browser — your inputs never leave your device, and nothing is uploaded or stored.
Worked example
For an 80 kg male at 18% body fat: lean mass = 80 × (1 − 0.18) = 65.6 kg.