Calculating your lean body mass is straightforward once you know the Lean Body Mass formula and what each input means. This guide explains the method in plain language, walks through a manual calculation, and gives worked examples you can follow — then you can do it instantly with the Lean Body Mass Calculator.
What is Lean Body Mass?
The Lean Body Mass calculation tells you your lean body mass from a few simple inputs. The figure you are solving for here is the lean body mass.
The Lean Body Mass formula
The core formula is:
Lean body mass = Body weight × (1 - Body fat percentage ÷ 100)Here is what each input means:
- Body weight — a value measured in kg. Example: 70 kg.
- Body fat percentage — a percentage, such as an annual rate. Example: 2%.
How to calculate it step by step
- Write down the body weight (for example, 70 kg).
- Write down the body fat percentage (for example, 2%).
- Apply the formula above to get your lean body mass.
- Double-check the result with the Lean Body Mass Calculator.
Worked examples
Example 1
| Input / Output | Value |
|---|---|
| Body weight | 70 kg |
| Body fat percentage | 2% |
| Lean body mass | 56.00 |
| Fat mass | 14.00 |
With body weight of 70 kg and body fat percentage of 2%, the lean body mass works out to 56.00.
Example 2
With body weight of 140 kg and body fat percentage of 2%, the lean body mass works out to 112.00.
| Result | Value |
|---|---|
| Lean body mass | 112.00 |
| Fat mass | 28.00 |
Example 3
With body weight of 35 kg and body fat percentage of 2%, the lean body mass works out to 28.00.
| Result | Value |
|---|---|
| Lean body mass | 28.00 |
| Fat mass | 7.00 |
Tips for an accurate result
- Keep your units consistent — mixing, say, months with years or grams with kilograms is the most common source of error.
- Round only at the very end. Rounding inputs early can shift the final answer noticeably.
- Re-run the numbers whenever an input changes, rather than estimating from an old result.
- These figures are general estimates, not medical advice — check with a qualified professional before acting on them.
Prefer not to do the maths by hand? — the Lean Body Mass Calculator does it instantly, for free, with the formula and a worked example built in.
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