FFMI Calculator
Enter your stats to calculate your Fat-Free Mass Index and muscularity category.
Fill in the form and hit calculate to see your results here.
Your Fat-Free Mass Index
—FFMI is only as accurate as your body fat % input — a rough estimate there will shift this result.
What FFMI measures
Fat-Free Mass Index adjusts your lean mass for height, similar to how BMI adjusts weight for height — it's a useful way to compare muscularity across different body sizes.
The 'natural limit' idea
Research on drug-tested lifters found normalized FFMI values rarely exceed about 25 for men without pharmacological assistance — a widely cited (though debated) reference point.
Why 'normalized'?
The normalized version adjusts for height so that someone very tall or very short isn't unfairly penalised or flattered by the raw calculation — it makes FFMI more comparable between people.
The formula
# Step 1 — Fat-free mass FFM(kg) = weight(kg) × (1 - bodyfat% / 100) # Step 2 — Raw FFMI FFMI = FFM(kg) / height(m)² # Step 3 — Normalized FFMI Normalized FFMI = FFMI + 6.1 × (1.8 - height(m))
Typical male ranges: below 18 (below average), 18-20 (average), 20-22 (above average), 22-25 (very muscular), 25+ (exceptional, approaching or above the natural range). Female ranges run roughly 4-5 points lower.
Common questions
For men, 20-22 is above average muscularity, and 22-25 is very muscular. For women, ranges sit roughly 4-5 points lower across the board.
The normalized version specifically adjusts for this — without it, taller lifters would appear to have lower muscularity even with the same relative development as someone shorter.
Not proof, but scores consistently above 25 (men) are uncommon in the drug-tested lifting population, so it's often used as one data point, not a definitive test.
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