FFMI (Fat-Free Mass Index) Calculator

Use this ffmi (fat-free mass index) calculator for an approximate adult fitness calculation. Choose US units for pounds, inches or yards, or switch to metric. Results are estimates, not medical or training prescriptions.

Your Numbers

Body Weightkg

Heightcm

Body Fat Percentage%

Results

FFMI—

Normalized FFMI—

Fat-Free Mass—

Input check—

Results update live as you type. Estimates only — not financial, tax, or investment advice.

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The Formula

FFMI = Lean Mass (kg) ÷ Height (m)²; Normalized FFMI = FFMI + 6.1 × (1.8 − height m)

Understanding the FFMI (Fat-Free Mass Index) Calculator

Worked example: At 85 kg (187.4 lb), 180 cm (70.9 in), and 15% body fat, fat-free mass is 72.25 kg and FFMI is 22.30.

FFMI depends on the accuracy of body-fat input. It cannot determine steroid use or a personal natural-muscle limit. Height normalization is a comparison convention.

Frequently Asked Questions

How is the result calculated?

FFMI = Lean Mass (kg) ÷ Height (m)²; Normalized FFMI = FFMI + 6.1 × (1.8 − height m)

What should I know about this estimate?

FFMI depends on the accuracy of body-fat input. It cannot determine steroid use or a personal natural-muscle limit. Height normalization is a comparison convention.