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FFMI Calculator
Estimate fat-free mass index using height, weight and body fat.
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FAQs
What is FFMI and what does it tell me?
Fat-Free Mass Index normalizes your lean mass to your height — like BMI, but for muscle instead of total weight. It's a better progress metric for lifters than scale weight because it separates muscle from fat.
What is a good FFMI score?
Roughly 18–20 is typical for trained men (16–18 untrained), and values approaching ~25 are commonly cited as near the natural ceiling. Women's values run lower on the same scale. Treat these as reference ranges, not verdicts — frame size and measurement error matter.
How accurate is the FFMI calculation?
It's only as accurate as your body-fat estimate. Consumer methods (scales, calipers) carry meaningful error, and water/glycogen shifts move lean mass day to day. Use the same measurement method consistently and track the trend, not single readings.