FFMI Calculator
FFMI (Fat-Free Mass Index) gauges how much lean mass you carry relative to your height — a better muscularity metric than BMI. Enter weight, height, and body-fat percentage.
How it works
Lean body mass
LBM = weight × (1 − bodyfat% ÷ 100)
FFMI
FFMI = LBM ÷ height(m)²
Normalized FFMI
normalized = FFMI + 6.1 × (1.8 − height in m), adjusting to a 1.8 m reference so tall and short lifters compare fairly.
Frequently Asked Questions
What is a good FFMI?
Around 18–20 is average, 20–22 is fit, 22–25 is very muscular. A normalized FFMI near ~25 is often cited as the natural muscular ceiling, though it varies by individual.
Is FFMI better than BMI?
For lifters, yes. BMI can't tell muscle from fat; FFMI uses your body-fat percentage to isolate lean mass.
Where do I get my body-fat percentage?
Use calipers, a DEXA scan, or a good estimate. FFMI is only as accurate as the body-fat figure you enter.
Building serious muscle?
Track every session and PR in GainLogger to keep the lean mass climbing. Free on iOS & Android.