FFMI Calculator
Find your fat-free mass index from height, weight and body fat, with the height-normalized value.
Your FFMI
22.0 kg/m²
- Normalized FFMI (to 1.8 m)
- 22.1 kg/m²
- Fat-free mass
- 153.0 lb
- Fat mass
- 27.0 lb
Your FFMI is 22, or 22.1 when normalized to a height of 1.8 m. Your fat-free mass is 153 lb.
Calculation breakdown
| Step | Formula | Result |
|---|---|---|
| Fat-free mass | 81.65 kg × (1 − 15%) | 69.40 kg |
| FFMI | 69.4 kg ÷ (1.778 m)² | 21.95 kg/m² |
| Normalized FFMI | 21.95 + 6.1 × (1.8 − 1.778) | 22.09 kg/m² |
How it works
Enter your height, weight and body fat percentage in imperial or metric units. The result updates as you type.
Worked example
An adult 1.80 m tall who weighs 90 kg with 15% body fat:
- Fat-free mass: 90 × (1 − 0.15) = 76.5 kg
- FFMI: 76.5 ÷ 1.80² = 76.5 ÷ 3.24 = 23.6
- Normalized FFMI: 23.6 + 6.1 × (1.8 − 1.8) = 23.6
For someone 1.75 m tall, weighing 80 kg with 12% body fat, FFMI is 70.4 ÷ 3.0625 = 22.99, and the normalized value is 22.99 + 6.1 × 0.05 = 23.29.
Sources
Frequently asked questions
What is FFMI?
FFMI, or fat-free mass index, is your fat-free mass in kilograms divided by your height in meters squared. It works like BMI but leaves out body fat, so it describes how much lean mass you carry for your height.
How is FFMI calculated?
First find fat-free mass as weight × (1 − body fat ÷ 100). Then divide it by height in meters squared. An adult who is 1.80 m tall, weighs 90 kg and has 15% body fat has 76.5 kg of fat-free mass and an FFMI of 23.6.
What is normalized FFMI?
Kouri and colleagues (1995) adjusted FFMI to a height of 1.8 m by adding 6.1 × (1.8 − height in meters). This lets people of different heights be compared. If you are exactly 1.8 m tall, the two numbers are the same.
Is an FFMI of 25 the natural limit?
In the 1995 study, normalized FFMI among men who did not use steroids stopped at about 25, while many users went past it. That was one small study of male athletes with estimated body fat, so it is a rough reference rather than a hard ceiling.
How accurate is my FFMI?
It depends mostly on your body fat percentage. Calipers, bioimpedance scales and visual estimates can be several percentage points off, which moves FFMI noticeably. A measured body fat figure, such as from a DEXA scan, gives a more reliable result.
FFMI is a rough measure of lean mass, not a diagnosis. This is information only, not medical advice.