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FFMI Calculator

Fat-free mass indexRuns locally · nothing uploaded

Normalized FFMI (to 1.8 m)
21.6
FFMI
21.5
BMI
25.2
Lean body mass
68 kg
Fat mass
12 kg

Reference: Kouri et al. (1995) studied 157 male athletes; the 74 who had never used steroids averaged a normalized FFMI of about 21.8, with a maximum near 25. The study included men only; women typically score clearly lower.

Also works as:ffmi calculatorfat free mass indexnatural limit ffmilean body mass calculator

How it works

Formula

Lean mass = weight × (1 − body fat)
FFMI = lean mass ÷ height²
Normalized FFMI = FFMI + 6.1 × (1.8 − height)

Worked example

Given: 178 cm, 80 kg, 15% body fat

  1. Lean mass = 68 kg.
  2. FFMI = 68 ÷ 1.78² ≈ 21.46; normalized ≈ 21.58.

Result: About 21.6, close to the drug-free average of 21.8 in Kouri et al.

Sources

  • Kouri EM, et al. Clin J Sport Med. 1995;5(4):223–228.

How to use

  1. 1Enter height and weight.
  2. 2Enter body fat percentage.
  3. 3Read FFMI, normalized FFMI and lean mass.

FAQ

How is FFMI different from BMI?

BMI counts muscle as excess weight; FFMI removes fat mass first, so it reflects muscularity.

Is 25 the natural limit?

In Kouri et al. (1995), drug-free male athletes topped out around 25. It's an observation, not a hard limit, and body-fat error shifts FFMI by 1–2 points.

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