Quick guide
How to use this calculator
- Use the labels and unit notes to enter the requested measurement, date, time, or observation exactly as recorded.
- Check the visible method, population, and unit basis before using the result; switch modes rather than converting values mentally.
- Read the calculation audit and limitations together. The result supports measurement or tracking and does not replace diagnosis, treatment, or urgent medical assessment.
Calculation method
How the adult body fat percentage calculator works
RFM = 64 - 20 × (height divided by waist circumference) + 12 × sex, where sex is 0 for the male equation and 1 for the female equation.
RFM is an empirical anthropometric estimate developed against DXA in a United States NHANES cohort aged 20-85 and independently validated in another NHANES cohort aged 20-69. This release uses the narrower validation age span. It is not a direct body-composition measurement and this page does not classify the result.
Worked example
Adult Body Fat Percentage example
For the male equation with height 180 cm and waist 90 cm, RFM estimates 24.0% body fat.
RFM = 64 - 20 × (height divided by waist circumference) + 12 × sex, where sex is 0 for the male equation and 1 for the female equation.
Supported inputs
Precision and limits
Supported purpose
Supported for ages 20-69. Accuracy varies by individual, age, body-fat range, population, and waist protocol. The binary sex variable reproduces the source model and is not a statement about gender identity. Pregnancy and use outside the validation age span are excluded.
Measurement quality
The output is only as reliable as the entered measurement, device, timing, units, and applicable reference population. Recheck unexpected values against the original record.
Clinical boundary
This calculator does not diagnose a condition, choose treatment, change medication, or determine that an urgent symptom is safe to monitor at home. Contact an appropriate health professional or local emergency service when the situation may be urgent.
Privacy
Entered health values and results stay in this browser tab. They are not placed in URLs, analytics, logs, local storage, session replay, or a cloud record by this calculator.
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