FFMI calculator
This FFMI calculator estimates your fat-free mass index from weight, height and body fat percentage, a better gauge of muscularity than BMI because it strips out fat mass entirely. Enter your stats, and see your normalized FFMI, adjusted to a 1.8 m reference height so lifters of different heights compare fairly, alongside your lean mass and where that number falls on a five-step band from low to the natural muscular limit.
Normalized FFMI
20.99
Above average
FFMI band
How it works
FFMI divides lean body mass, weight minus estimated fat mass, by height in metres squared, the same shape as BMI but built only from the fat-free portion of the body (Kouri 1995). Because taller people naturally carry more lean mass for the same leanness, the normalized version adds a small correction, 6.1 times the gap between 1.8 m and your height, so two people of different heights with the same muscularity land at a similar number.
Kouri's original research found that drug-free male lifters rarely exceeded a normalized FFMI of about 25, making that figure a commonly cited, if imperfect, marker of the natural muscular ceiling. Individual genetics, bone structure and measurement error in body fat all shift where any one person actually sits.
Body fat percentage is the input most likely to be wrong: skinfold, bioimpedance and DEXA methods can disagree by several percentage points on the same person, and that error carries directly into both lean mass and FFMI.
Frequently asked questions
What is a good FFMI?
A normalized FFMI around 20 is average for an untrained adult male, 22 to 25 is a well-built, experienced lifter, and above 25 is rare without performance-enhancing drugs. Bands for women sit a few points lower given typical differences in muscle mass.
Why does FFMI adjust for height?
Lean mass scales with height even at the same relative muscularity, so a tall and a short lifter with identical body composition would otherwise show different FFMI scores. The normalized version corrects for that by adjusting every result to a common 1.8 m reference height.
How accurate is a home body fat estimate for this calculator?
Home methods like skinfold calipers or scale-based bioimpedance typically carry several percentage points of error, which shifts the FFMI result noticeably. Use this as a rough estimate and track the trend over months rather than treating one reading as exact.
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These values are training estimates. They are not medical advice.
Overload syncs your weight and body fat automatically
Connect your health app and Overload pulls in weight and body fat trends automatically, so your FFMI stays current without manual entry. Free on iOS and Android.