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Fat Free Mass Index Calculator

Work out fat free mass index instantly with clear inputs, formula shown and shareable results.

About Fat Free Mass Index Calculator

FFMI applies the BMI idea to lean mass alone, so it measures muscularity rather than total size. An 80 kg man at 15% fat and 1.78 m carries 68 kg of lean mass, giving an FFMI of 21.5 and a height-normalised 21.6. Values above 25 normalised are very rarely achieved without pharmacological assistance.

Formulas

Fat-free mass index

FFMI = fat-free mass / height(m)^2

Height normalisation

normalised = FFMI + 6.1 x (1.8 - height in m)

Worked example

With the default values below, Fat Free Mass Index Calculator returns Fat-Free Mass Index of 21.46. Change any input above and every figure here is recalculated in your browser.

Inputs used

Body weightminimum 1 kg
80 kg
Body fat percentageaccepts 0–70 %
15 %
Heightminimum 100 cm
178 cm

Results

Fat-Free Mass Index
21.46 kg/m2
Fat-Free Mass
68.00 kg
Height-Normalised FFMI
21.58
Muscularity Assessment
Above average muscularity

Step by step

  1. 1Values used
  2. 2Fat-free mass index
  3. 3Height normalisation
  4. 4Fat-Free Mass Index= 21.46 kg/m2
  5. 5Fat-Free Mass= 68.00 kg
  6. 6Height-Normalised FFMI= 21.58
  7. 7Muscularity Assessment= Above average muscularity

Assumptions and limits

  • The result is derived only from the 3 inputs listed above. Anything not among them is not part of the calculation.
  • In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
  • Figures are rounded for display to 2 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.
  • These figures are population-average estimates, not a medical assessment or diagnosis. Body composition equations carry errors of several percentage points, and healthy ranges vary with age, ethnicity, muscularity and medical history. Discuss weight or body composition goals with a qualified clinician or dietitian.
  • This is an estimate for general information and not professional medical advice. See the full disclaimer for the limits that apply to this kind of calculator.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

These figures are population-average estimates, not a medical assessment or diagnosis. Body composition equations carry errors of several percentage points, and healthy ranges vary with age, ethnicity, muscularity and medical history. Discuss weight or body composition goals with a qualified clinician or dietitian.

Frequently Asked Questions

What FFMI is achievable naturally?

Most drug-free men plateau around 22-23 normalised, with 25 considered the practical natural ceiling in the original Kouri study.

Why normalise for height?

Because the squared denominator still favours shorter people slightly, and the 6.1 correction removes that residual bias.

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