Lean Body Mass Calculator
Everything that isn't fat: muscle, bone, organs and water.
Enter your values
Choose one of: Metric (kg, cm), Imperial (lb, in).
Enter the weight you are working with.
Enter the height you are working with.
Choose one of: Male, Female.
Results update instantly as you type — no submit needed. Your values are remembered on this device, and the shareable link reopens the calculator with exactly these numbers.
- Lean body mass
- 130 lb
- Fat mass
- 40 lb
- Body fat
- 23.5%
- Fat-free mass index
- 19.2
Quick answer
Lean body mass is total weight minus fat mass; the Boer formula estimates it from height and weight alone.
Male LBM = 0.407·kg + 0.267·cm − 19.2
At a glance
| What it does | Everything that isn't fat: muscle, bone, organs and water. |
|---|---|
| Category | Health |
| Inputs needed | Units, Weight, Height, Sex |
| Main output | Lean body mass |
| Formula | Male LBM = 0.407·kg + 0.267·cm − 19.2 |
| Cost | Free — no sign-up, no download |
How to use the Lean Body Mass Calculator
- 1Choose your units.
- 2Enter weight, height and sex.
- 3Read lean mass and estimated fat mass.
Inputs explained
- Units
- Choose one of: Metric (kg, cm), Imperial (lb, in).
- Weight
- Enter the weight you are working with.
- Height
- Enter the height you are working with.
- Sex
- Choose one of: Male, Female.
Worked example
Using the values the calculator loads with:
Inputs
- UnitsImperial (lb, in)
- Weight170
- Height69
- SexMale
Results
- Lean body mass130 lb
- Fat mass40 lb
- Body fat23.5%
- Fat-free mass index19.2
Frequently asked questions
Why track lean mass?
During a diet it shows whether you are losing fat or muscle, which weight alone cannot tell you.
What is a good FFMI?
Around 19–21 for trained men and 15–17 for trained women; above 25 without drugs is very rare.
What do I need to enter into the Lean Body Mass Calculator?
Just 4 values: units, weight, height, sex. Every field starts with a realistic example, so you can change one number at a time and watch the result update instantly.
How does the Lean Body Mass Calculator work out the answer?
Lean body mass is total weight minus fat mass; the Boer formula estimates it from height and weight alone. It applies the formula Male LBM = 0.407·kg + 0.267·cm − 19.2 and shows the working so you can check each step by hand.
Is the Lean Body Mass Calculator free, and do I need an account?
It is completely free with no sign-up, no download and no usage limit. Everything is calculated in your browser, so the numbers you type never leave your device.
Results are estimates for general information. For medical, legal, structural or financial decisions, confirm with a qualified professional.