What this calculator does
Fat-free mass index (FFMI) works out muscularity measure that adjusts fat-free mass for height, comparable across body sizes. Enter your own figures above and the answer updates as you type: nothing is fixed in the code, so the result reflects exactly the numbers you supply.
The formula this calculator evaluates is printed under the tool and explained below, so you can check the working by hand or reuse it in a spreadsheet.
The formula
FormulaFFMI = lean mass(kg) / height(m)²; normalized FFMI = FFMI + 6.1 × (1.8 − height(m))
The inputs explained
| Field | What to enter |
|---|---|
| Lean (fat-free) mass (kg) | A number, measured in kg. Starts at 60. |
| Height (cm) | A number, measured in cm. Starts at 175. |
Worked examples
Every figure in the tables below is produced by this page’s own calculator at build time, so the numbers and the tool always agree. Select any row to load that scenario.
How the answer changes with lean (fat-free) mass
Every other input is held at the calculator’s starting values while lean (fat-free) mass varies. Select any row to load that scenario into the calculator.
How the answer changes with lean (fat-free) mass
| Lean (fat-free) mass (kg) | FFMI | Normalized FFMI (to 1.8 m) | Typical natural range |
|---|---|---|---|
| 30 | 9.8 | 10.1 | 18 - 25 (higher is more muscular) |
| 45 | 14.7 | 15.0 | 18 - 25 (higher is more muscular) |
| 60 | 19.6 | 19.9 | 18 - 25 (higher is more muscular) |
| 90 | 29.4 | 29.7 | 18 - 25 (higher is more muscular) |
| 120 | 39.2 | 39.5 | 18 - 25 (higher is more muscular) |
| 180 | 58.8 | 59.1 | 18 - 25 (higher is more muscular) |