Body Fat Calculator (Navy Method)

Estimating body fat percentage through the US Navy circumference method gives you a quick, equipment-light read on body composition using nothing more than a tape measure. The number carries real health meaning: CDC lists type 2 diabetes, coronary heart disease and many types of cancer among the conditions linked to overweight and obesity. It also tracks fitness progress more honestly than scale weight alone, since two people at the same weight can carry very different amounts of fat.

The calculator uses the circumference equations printed in Department of Defense Instruction 1308.3 (2002), with every measurement in inches. For men: body fat % = 86.010 × log10(waist − neck) − 70.041 × log10(height) + 36.76, with the waist measured at the navel. For women: 163.205 × log10(waist + hip − neck) − 97.684 × log10(height) − 78.387, with the waist measured at its narrowest point. The equations return a percentage directly; the calculator then multiplies it by your weight to split out fat mass and lean mass.

Accuracy depends on technique, so take each measurement the same way every time, ideally with the same person measuring and at a consistent hour of the day. Skip readings right after hard exercise or a large meal, both of which can briefly distort your dimensions. The method is dependable for everyday tracking, but it remains an estimate and will not match the precision of lab-based tools such as a DEXA scan.