# FFMI Calculator (Fat-Free Mass Index)

URL: https://speedycalculator.com/calculators/health/ffmi/
Last updated: 2026-10-25

> The FFMI calculator measures muscularity relative to height. It combines weight, height and body fat percentage into a fat-free mass index, with a height-normalised value used to compare people of different heights.

## Inputs

- Weight (kg, lb, g, oz, st)
- Height (cm, m, mm, in, ft)
- Body fat (%)

## Results

- Fat-free mass
- FFMI
- Normalised FFMI

## Formula

```
Fat-free mass = W × (1 − BF%)
FFMI = FFM ÷ height²
Normalised FFMI = FFMI + 6.1 × (1.8 − height m)
```

## Explanation

Unlike BMI, FFMI separates muscle from fat. Values above about 25 are uncommon in men without performance-enhancing drugs, according to a 1995 study.

### How to use the FFMI Calculator

- **Weight**
- **Height**
- **Body fat**

Results update as you type, and every field accepts the units shown in its menu.

### How it works

Remove fat mass from weight, then divide by height in metres squared.

### Inputs explained

FieldWhat to enterWeightUnits: kg, lb, g, oz, stHeightUnits: cm, m, mm, in, ftBody fatIn %

### What each result means

- **Fat-free mass** = [Weight] × (1 - [Body fat]÷100)
- **FFMI** = [Fat-free mass] ÷ ([Height]÷100)^2
- **Normalised FFMI** = [FFMI] + 6.1×(1.8 - [Height]÷100)

### Example values

How the main result changes when **Weight** changes and everything else stays at the example values above:

Weight (kg)Normalised FFMI4110.861.516.18221.5102.526.912332.316443
*Health note: this calculator is for education and screening only and is not a diagnosis or treatment advice. Discuss your results with a qualified clinician.*

## Worked example

Inputs — Weight: 82 kg; Height: 180 cm; Body fat: 15 %.

Results — Fat-free mass = 69.7 kg; FFMI = 21.5; **Normalised FFMI = 21.5**.

## FAQ

**What is a typical FFMI?**
Around 18–20 for untrained men and 14–17 for untrained women.

**How do I get body fat %?**
Use the body fat calculator or a body composition scan.

**What formula does the FFMI Calculator use?**
Fat-free mass = W × (1 − BF%).


## Sources

- [Kouri EM et al. Fat-free mass index in users and nonusers of anabolic-androgenic steroids. Clin J Sport Med, 1995](https://pubmed.ncbi.nlm.nih.gov/8882103/)