Relative Fat Mass Body Fat Calculator
Estimate adult body-fat percentage with the published height/waist Relative Fat Mass equation and explicit coefficient selection.
YOUR CALCULATION
Result
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Calculation steps
Work through one step at a time or reveal the complete calculation. The steps use your current inputs.
How to calculate
Convert height and waist to the same unit and apply the published adult RFM anthropometric model.
RFM=64−20×height/waist+12×sex coefficient
Worked example
Height 175 cm and waist 85 cm with male coefficient 0 give RFM about 22.8%. The displayed value is rounded to one decimal place.
Assumptions and input details
The original 2018 cross-sectional study used US adult NHANES data and DXA comparison. Waist measurement site matters: use the study/NHANES waist convention, not an interchangeable narrowest-waist measurement. This is an estimate, not measured body composition, a diagnosis or an intake/training target. No child or pregnancy interpretation is provided; outputs outside 0–100% are rejected as uninterpretable.
References: Original RFM study: equation, measurements and validation scope
Unit definitions
Unit selection is independent of language. Each selector contains only units for its physical quantity. Calculations use defined base units internally.
Choose from 23 length definitions, including explicitly labelled regional measures. Area conversions square the length factor; geometric volumes cube it.
Regional measures are not interchangeable merely because their names look similar. This is a documented selection, not a claim to include every historical unit.
NIST measurement tables · Japanese traditional units · Mainland China and Hong Kong unit distinctions
Using this calculator
Can I enter my own problem?
Yes. Replace the example values with your own inputs. The result, calculation steps, tables and applicable diagrams update from those inputs. Blank or invalid values clear the result; example values are never silently substituted for missing inputs.
Are the results exact?
Results use floating-point arithmetic and displayed rounding. Read the formula, assumptions and any stated data precision before interpreting the result.
Is my input uploaded?
The calculation runs in your browser. No account, file upload or external AI service is required. Inputs are not saved between page reloads.
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