FFMI calculator
FFMI = fat-free mass ÷ height². Example: 168 cm, 76 kg and 14% body fat give 23.2, or 23.9 height-adjusted.
How it is worked out
For the example above (168 cm, 76 kg, 14% body fat):
- Fat-free mass = weight × (1 − body fat): 76 × 0.86 = 65.36 kg
- FFMI = fat-free mass ÷ height²: 65.36 ÷ 1.68² = 23.16
- Normalised FFMI = FFMI + 6.3 × (1.80 − height in m): 23.16 + 6.3 × 0.12 = 23.91
Your body fat figure is an estimate whatever the method, and it moves the result: here, 3 points either way changes FFMI by about 0.8.
6.3 or 6.1?
Kouri et al. (1995) describe the height adjustment as a correction of 6.3 × (1.80 m − height).
Many calculators use 6.1. We default to the paper’s 6.3 and let you switch. The two differ by less than 0.05 for most heights:
| Height | 6.3 adds | 6.1 adds |
|---|---|---|
| 160 cm | +1.26 | +1.22 |
| 168 cm | +0.76 | +0.73 |
| 180 cm | 0 | 0 |
| 190 cm | -0.63 | -0.61 |
What FFMI can and can’t tell you
FFMI is a ratio of lean mass to height. It is only as good as the body fat estimate you enter, and different methods give different estimates. It is not a verdict on anyone, and it says nothing about how a person trains.
Source: Kouri EM, Pope HG, Katz DL, Oliva P. Clin J Sport Med 1995;5(4):223-8 (PMID 7496846), abstract read in November 2026.
Questions
What is a normalised FFMI?
FFMI adjusted to a height of 1.80 m, so people of different heights can be compared. Shorter people get a small addition, taller people a small subtraction.
Can I use pounds and inches?
Yes. Press lb: weight is then in pounds and height in inches. The result is the same.
Is anything I type sent to you?
No. The calculator runs in your browser and nothing you enter leaves your device.