FFMI (Fat-Free Mass Index)
A measure of muscle mass relative to height, similar to BMI but for lean mass.
Updated
FFMI is calculated as fat-free mass (kg) divided by height squared (m²). It provides a normalized measure of muscularity. Natural lifters typically max out around FFMI 25-26. Values above 25 are considered very muscular; above 27-28 strongly suggest performance-enhancing drug use. FFMI is useful for setting realistic expectations.
Work yours out: FFMI calculator
What the number means
FFMI is fat-free mass in kilograms divided by height in metres squared, and the version most calculators report adds 6.3 × (1.80 − height in metres) so that short and tall lifters can be compared on the same scale. Untrained adult men tend to sit somewhere around 18 to 20 and untrained women around 14 to 17, and years of consistent training typically moves men into the low 20s. The often-quoted ceiling of 25 comes from Kouri and colleagues in 1995: among 157 male athletes, the drug-free ones topped out at a normalised 25.0, and a sample of Mr America winners from before the steroid era averaged 25.4.
Working it out
Take an 80kg lifter, 1.78m tall, at an estimated 15 per cent body fat. Fat-free mass is 80 × 0.85 = 68kg. Height squared is 3.17, so FFMI is 68 ÷ 3.17 = 21.5, and the height correction adds about 0.1, giving roughly 21.6. The useful thing to do with that figure is track it over time with the same measuring method, because a rising FFMI at a stable body-fat estimate is a reasonable sign that lean mass is accumulating rather than fat.
Limitations
The whole calculation rests on a body-fat estimate, and that is the weak link. Bioimpedance scales, callipers and visual estimates can each be several percentage points out; in the example above, 18 per cent body fat instead of 15 drops the FFMI from 21.5 to 20.7. Fat-free mass also includes bone, organs, water and stored glycogen, not only muscle, so a heavy-framed or well-hydrated lifter reads higher. The Kouri study itself was small, all male and described by its authors as preliminary, and there is far less comparable data for women.
What it cannot tell you
A figure above 25 is a reason for curiosity, not proof of drug use. A handful of drug-free lifters, particularly those carrying more body fat or measured with a generous method, will exceed it, and plenty of enhanced lifters sit below it. Used on yourself, FFMI is a reasonable way to set long-term expectations and to notice when progress has genuinely slowed. Used to judge other people from a photograph and a guessed body-fat percentage, it is two estimates multiplied together and presented as a verdict.
Examples
- FFMI = FFM (kg) / height (m)²
- Natural limit around 25-26
- Measures muscularity
Compound exercises
Put this into practice with exercises from the library.
Plie Dumbbell Squat
Strength · Dumbbell
Plyo Kettlebell Pushups
Strength · Kettlebells
Plyo Push-up
Plyometrics · Bodyweight
Power Clean
Strength · Barbell
Power Clean from Blocks
Olympic Weightlifting · Barbell
Power Jerk
Olympic Weightlifting · Barbell
Power Snatch
Olympic Weightlifting · Barbell
Power Snatch from Blocks
Olympic Weightlifting · Barbell
Common questions
What is FFMI?
A measure of muscle mass relative to height, similar to BMI but for lean mass. FFMI is calculated as fat-free mass (kg) divided by height squared (m²).
What exercises train the FFMI?
Good options include Plie Dumbbell Squat, Plyo Kettlebell Pushups, Plyo Push-up, Power Clean, Power Clean from Blocks. Each links to a step-by-step guide with demonstration images.
What are examples of FFMI?
FFMI = FFM (kg) / height (m)²; Natural limit around 25-26; Measures muscularity.
Put it into practice
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