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Relative Fat Mass Calculator

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

About Relative Fat Mass Calculator

Relative fat mass needs only height and waist: RFM = 64 - 20 x (height/waist) for men, with 76 replacing 64 for women. A 175 cm man with an 88 cm waist gives 24.2%. Published against DEXA on NHANES data, it estimates body fat percentage more accurately than BMI, particularly for women.

Formulas

Relative fat mass, men

RFM = 64 - 20 x (height / waist)

Relative fat mass, women

RFM = 76 - 20 x (height / waist)

Worked example

With the default values below, Relative Fat Mass Calculator returns Relative Fat Mass of 24.23%. Change any input above and every figure here is recalculated in your browser.

Inputs used

Heightminimum 100 cm
175 cm
Waist circumferenceminimum 30 cm
88 cm
Sexone of Male, Female
Male

Results

Relative Fat Mass
24.23%
Height To Waist Ratio
1.989
Category
Above healthy range
Note
RFM was validated against DEXA and outperforms BMI for estimating fat percentage

Step by step

  1. 1Values used
  2. 2Relative fat mass, men
  3. 3Relative fat mass, women
  4. 4Relative Fat Mass= 24.23
  5. 5Height To Waist Ratio= 1.989
  6. 6Category= Above healthy range
  7. 7Note= RFM was validated against DEXA and outperforms BMI for estimating fat percentage

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 3 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

Why is RFM better than BMI?

Because it uses waist rather than weight, so it captures fat distribution and does not misclassify muscular people as over-fat.

Must height and waist share units?

Yes - the ratio must be dimensionless, so use centimetres for both or inches for both.

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