Lean Body Mass Calculator
Enter your sex, height and weight (optionally your body fat percentage) to estimate your lean body mass and fat mass. Works in metric or imperial units.
← Back to all toolsWant your body fat percentage? →Enter your details to see your lean body mass and fat mass.
What is lean body mass?
Lean body mass (LBM) is your body weight minus fat — including muscle, bone, organs and water.
LBM is a more meaningful body-composition measure than weight alone, used to track training progress and metabolic health.
How we calculate it
We offer two methods: the body-fat method when you know your body fat percentage (more accurate), otherwise the Boer formula:
| Item | Calculation |
|---|---|
| Body-fat method | LBM = weight × (1 − body fat %) |
| Boer formula (men) | 0.407 × weight + 0.267 × height − 19.2 |
| Boer formula (women) | 0.252 × weight + 0.473 × height − 48.3 |
Keep in mind
These are estimates. Interpret with care for:
- Athletes and very muscular people (may be overestimated)
- Older adults (body composition changes with age)
- Edema or dehydration (changes the reading)
- The Boer formula and body-fat method can differ
Frequently asked questions
What is lean body mass?
Lean body mass is your body weight minus fat — muscle, bone, organs and water. It is an important measure of body composition.
How is LBM related to body fat percentage?
They are complementary: body fat percentage is the fat share of your weight, and LBM is the rest. Knowing body fat percentage gives an exact LBM.
Why are there two results?
The Boer formula estimates from height and weight only; the body-fat method needs your body fat percentage but is more accurate. Compare both as a cross-check.
Is higher lean body mass better?
Higher LBM usually means more muscle and a higher resting metabolism, which helps long-term weight management.
Does this calculator store my data?
No. All calculations run locally in your browser and nothing is uploaded or saved.