This uses the U.S. Navy body fat estimation formulas (widely used and suitable for quick estimation). The calculator expects measurements in the chosen units — if you enter inches the calculator converts them to centimeters internally. Calculation happens only when you press Calculate Body Fat %.

Formulas used:

Male:   BF% = 86.010 * log10(waist - neck) - 70.041 * log10(height) + 36.76
Female: BF% = 163.205 * log10(waist + hip - neck) - 97.684 * log10(height) - 78.387
          

Important: These are estimates. For medical/diagnostic purposes consult a professional. Accuracy varies with measurement technique, body shape and population.