Calculator
FFMI Calculator
Quick answer
FFMI is fat-free mass in kilograms divided by height in metres squared. Fat-free mass is body weight times (1 − body fat percent).
The normalized figure adds 6.3 × (1.80 − height in metres), which is the adjustment printed in Kouri and colleagues, 1995. Some calculators use 6.1. This one follows the paper.
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Estimates only. Testing a true max carries risk; use a spotter or safety arms. Not medical advice.
Normalized (Kouri 6.3 × (1.80 − height)): 23.6. Lean mass 76.5 kg.
On this page
How does the FFMI calculator work?
Lean mass = weight × (1 − body fat / 100). FFMI = lean mass / height². Both weight and lean mass are in kilograms. Height is converted from centimetres.
Normalized FFMI = FFMI + 6.3 × (1.80 − height). At exactly 1.80 m the two numbers match. Taller people are adjusted down, shorter people up, so the index is closer to a 1.80 m frame.
What inputs does it need?
Height in centimetres, weight, and a body-fat percent. The body-fat number is the weak input. A cheap scale and a DEXA will not agree, and the index moves with them.
Pounds are converted before the division. Do not convert twice.
Worked example with sample numbers
Example only: 1.80 m, 90 kg, 10% body fat. Lean mass is 81 kg. FFMI is 81 / 3.24 = 25.0. Normalized FFMI is also 25.0 because the height term is zero.
The 1995 paper reported that, in its sample of male athletes who had not used steroids, normalized FFMI reached up to about 25, and called the finding preliminary. It is not a medical cutoff, and it is not a women's standard. The paper's sample was men.
Common mistakes
Treating 25 as a law of nature. It is an observation from one sample, with estimated body composition on some historical athletes. Read what FFMI is before you quote it at someone.
Using a body-fat percent you do not believe. The index is only as good as that percent. A 3-point error in body fat moves lean mass more than most people expect.
FAQ
What is a normal FFMI?
The calculator does not assign a normal range. Population averages depend on the measurement method. The 25 figure in Kouri 1995 is an upper region in that study's non-users, not a target.
Why 6.3 and not 6.1?
The 1995 abstract says the authors added 6.3 × (1.80 m − height). 6.1 shows up on other calculators. This page follows the paper.
Does this detect steroid use?
No. The original paper discussed the index as a possible screen and called the work preliminary. A calculator result is not a test.
Is FFMI the same as BMI?
No. BMI uses total weight. FFMI uses an estimate of weight minus fat.
What if I do not know my body fat?
Then you cannot compute FFMI honestly. BMI is a different number and this page will not substitute it.