Body Fat Calculator

What this calculator does

Estimate body fat from circumference measurements in inches. Invalid measurements produce an error, and fat mass is displayed in pounds.

How to use the calculator

Use the inputs and units named in this form. Select Calculate after changing the values.

How the calculation works

The implemented male formula is 86.010 x log10(waist - neck) - 70.041 x log10(height) + 36.76. The female formula is 163.205 x log10(waist + hip - neck) - 97.684 x log10(height) - 78.387. All circumferences and height must be in inches. Fat mass is body weight in pounds multiplied by the estimated percentage divided by 100.

Worked example

Using the male formula with height 70 in, neck 15 in, waist 36 in and weight 180 lb gives about 21.25%, or 38.3 lb estimated fat mass. Hip circumference is not used by the male formula.

How to interpret the result

Compare the result with the assumptions and units shown above. The calculation uses the values entered into this page.

Assumptions and limitations

This is a circumference-based estimate from the formulas shown, not a clinical measurement. Measurement technique and body proportions affect it. The tool no longer assigns a health category from one set of cutoffs for everyone. A calculated status means the arithmetic succeeded, not that a clinician validated the result.

Common mistakes

Check the units and time period before calculating. An error message means the result cannot be calculated from the current inputs.

Privacy

The calculation runs in your browser. This form needs the numerical inputs shown, not names, account numbers or passwords.

Frequently asked questions