FFMI & Natural Muscular Potential Calculator
Calculate Fat-Free Mass Index (FFMI) and normalized height-adjusted FFMI to assess lean muscular development, compare against the 25.0 natural genetic limit, and predict maximum lean body mass.
Body Measurements
kg
%
cm
Muscularity Classification
ADVANCED NATURAL ATHLETE
Normalized FFMI (Height-Adjusted)
23.1
Standardized to 1.80m stature
Raw FFMI
23.1
Fat-Free Mass / Height²
Fat-Free Mass (Lean Mass)
74.8 kg
10.2 kg fat mass (12.0%)
Maximum Natural Potential (at 10% BF)
89.0 kg
Kouri 25.0 ceiling benchmark
Kouri et al. Scientific Muscularity Scale
18.0 – 20.0:
Average untrained individual
20.0 – 22.0:
Regular resistance training / athletic
22.0 – 24.0:
Advanced natural bodybuilder
24.0 – 25.0:
Elite natural genetic potential
> 25.0:
Unlikely natural (<0.1% of population)
Height Normalization Formula
Clinical Sports Medicine
Raw FFMI tends to underestimate the muscularity of shorter individuals and overestimate taller athletes. The normalized formula, FFMI_norm = FFMI + 6.1 × (1.80 - Height_m), normalizes every lifter to a standardized 1.80 m (5 ft 11 in) stature.