This fat free mass index calculator finds your FFMI — muscle mass relative to height — from lean body mass and height. Enter the values above.
Formula
FFMI = Lean body mass(kg) ÷ height(m)² Adjusted FFMI = FFMI + 6.1 × (1.8 − height in m)
Example
LBM 61.4 kg, height 1.8 m: FFMI = 61.4 ÷ 1.8² = 18.95.
Typical FFMI
Around 18-20 is average for men, with natural trained lifters often reaching the low-to-mid 20s.
Important
This tool is for general educational purposes only and is not medical advice, diagnosis, or treatment. It does not replace evaluation by a qualified healthcare professional — consult one for any health decision. Last updated: August 2026.
Frequently Asked Questions
What is fat-free mass index?
It measures muscularity by dividing lean body mass by height squared, like BMI but for lean mass instead of total weight.
How do I calculate FFMI?
Divide lean body mass in kg by height in meters squared; an adjusted version normalizes for height.
What FFMI is achievable naturally?
Many experts cite a natural ceiling around 25, though individual genetics vary.