FFMI Calculator

The fat-free mass index (FFMI) is like BMI, but uses only fat-free mass, so it reflects muscle rather than total weight. Gym-goers use it to track muscle gain.

Height in
Weight in
Use the body fat calculator if you do not know it.
Results update as you type.

FFMI (adjusted for height)

19.9

Average

FFMI
19.3
Fat-free mass
55.8 kg

The bands above are commonly used for men; values for women run about 3 to 4 points lower.

About this calculator

Enter your height, weight and body fat percentage. The adjusted FFMI corrects for height so tall and short people can be compared.

How to use it

  1. Enter height and weight.
  2. Enter body fat percentage.
  3. Read FFMI and adjusted FFMI.

The formula

FFMI = fat-free mass ÷ height²; adjusted FFMI = FFMI + 6.1 × (1.8 − height in m)
fat-free mass
weight × (1 − body fat %)
height
in metres

Worked example

170 cm, 68 kg, 18% body fat

  1. Fat-free mass = 68 × 0.82 = 55.8 kg.
  2. FFMI = 55.8 ÷ 1.7² = 19.3; adjusted = 19.9.
  3. That is in the average range for men.

What the result means

Most men without years of training are around 18 to 20; 22 or more reflects a lot of muscle.

Assumptions

  • Body fat percentage is reasonably accurate.

Limitations

  • The result is only as good as the body fat estimate.

Frequently asked questions

What is a good FFMI?

For men, about 20 to 22 is above average and 22 to 25 is very muscular.

Is FFMI different for women?

Yes, typical values are about 3 to 4 points lower.

How do I find my body fat?

Use the body fat calculator with a tape measure.

Not medical advice. This calculator is a general screening tool and cannot diagnose any condition. Results are estimates. Please talk to a doctor or a qualified health professional about your health and before making changes to diet, exercise or treatment.

Last reviewed on 1 October 2026. Found a mistake? Tell us.