Estimate body fat percentage using circumference measurements and the Wilmore and Behnke (1974) anthropometric equations, a field method used when DEXA or hydrostatic weighing is unavailable.
Inputs
The tool uses height, sex, and circumferences (neck, waist, and hip for women; neck and waist for men). Measure at consistent anatomical landmarks—typically at the narrowest waist, widest hip, and mid-neck with the tape horizontal.
How it differs from BMI
Body fat percentage estimates adiposity directly rather than inferring it from weight and height alone. It can better reflect composition changes during strength training when scale weight is stable.
Limitations
Circumference methods assume typical fat distribution and can over- or under-estimate in athletes, older adults, and people with significant visceral fat. Measurement technique (tape tension, time of day, hydration) shifts results by several percentage points. Equations are population averages, not individual diagnostics.
Health disclaimer
Body fat estimates are for general fitness awareness, not medical diagnosis. Consult a healthcare or fitness professional for clinical body-composition assessment, especially if you manage eating disorders, metabolic conditions, or pregnancy.
When to use it
Use this body/fat when you need a quick, private calculation in the browser without uploading data to a server—helpful for learning, prototyping, and everyday checks.
Example
For example, enter the default sample values on the form and compare the output with a known reference; adjust one input at a time to see how the result changes.