Health & Fitness
Fat-Free Mass Index Calculator
Calculate FFMI and compare it with the commonly cited natural muscular limit.
Preparing your result…
What this calculator does
Calculates Fat-Free Mass Index Calculator using the formula verified against the cited source.
What your result means
An estimate from the inputs you enter, within the scope stated below — not advice.
Formula
FFM = weight × (1 − BF% ÷ 100); FFMI = FFM ÷ height²; normalised FFMI = FFMI + 6.3 × (1.80 − height in m) (Kouri 1995)
The step-by-step working for your own numbers appears with the result above and in the PDF report.
Frequently asked questions
Symbols and assumptions
- Inputs
- The values entered in the fields above
- • FFM kg=body kg×(1−BF%/100); FFMI=FFM/height m². Kouri height-normalized FFMI=FFMI+6.3×(1.80−height m).
Sources and review
Reviewed 2026-10-18 · Next review 2027-04-18
- • Original Kouri paper uses 6.3, whereas supplied formula uses 6.1. Distinguish raw and normalized FFMI. The observed value near 25 in this male-athlete sample is not a universal biological ceiling or a diagnostic test for drug use.
Important limitation
This is an educational estimate based only on the values and formula shown. Verify current rates, rules, units, and professional standards before relying on the result. It is not personalized financial or investment advice.
Quick reference
| Scenario | Weight (kg) | Height (m) | Body fat (%) | Fat-free mass index (FFMI) |
|---|---|---|---|---|
| Worked example | 80 | 1.78 | 15% | 21.4619 kg/m² |
| Half the amounts | 40 | 1.2 | 7.5% | 25.6944 kg/m² |
| Double the amounts | 160 | 2.2 | 30% | 23.1405 kg/m² |
Need the full picture? Get the detailed PDF report with charts, tables, formulas and working steps.
Reviewed 2026-10-18 · Next review 2027-04-18
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