What this calculator does
Relative fat mass (RFM) works out body fat percentage estimated from height and waist circumference (Woolcott-Bernstein formula). Enter your own figures above and the answer updates as you type: nothing is fixed in the code, so the result reflects exactly the numbers you supply.
The formula this calculator evaluates is printed under the tool and explained below, so you can check the working by hand or reuse it in a spreadsheet.
The formula
FormulaMen: RFM = 64 − 20 × (height / waist); Women: RFM = 76 − 20 × (height / waist)
The inputs explained
| Field | What to enter |
|---|---|
| Height (cm) | A number, measured in cm. Starts at 175. |
| Waist circumference (cm) | A number, measured in cm. Starts at 85. |
| Sex | Choose from Male, Female. |
Worked examples
Every figure in the tables below is produced by this page’s own calculator at build time, so the numbers and the tool always agree. Select any row to load that scenario.
How the answer changes with height
Every other input is held at the calculator’s starting values while height varies. Select any row to load that scenario into the calculator.