Body Fat Percentage Calculator

The US Navy Method Formula

This tool uses the US Navy circumference method, which estimates body fat from tape measurements and height rather than skinfold calipers. For men the formula is %BF = 495 / (1.0324 − 0.19077 × log10(waist − neck) + 0.15456 × log10(height)) − 450. For women it adds the hip measurement: %BF = 495 / (1.29579 − 0.35004 × log10(waist + hip − neck) + 0.22100 × log10(height)) − 450. All lengths use the same unit (inches in the original equation; the tool handles metric conversion for you).

How to Measure Correctly

Accuracy depends entirely on good measurements. Use a flexible tape, keep it level and parallel to the floor, and pull it snug without denting the skin. Measure the neck just below the Adam's apple, the waist across the navel (men) or at the narrowest point (women), and the hips at the widest point of the buttocks. Take each measurement twice and average them — a half-inch error at the waist can shift the estimate by more than a full percent.

Interpreting Your Result

Body fat percentage tells you what portion of your total weight is fat versus lean mass (muscle, bone, water, organs). Two people can weigh the same yet look very different because one carries more muscle. That is why body fat is often a more useful goal than the number on the scale: dropping from 24% to 18% while holding weight steady means you traded fat for muscle. Track the trend across weeks rather than fixating on a single reading.

Limitations and When to Seek Professional Testing

The Navy method assumes an average body-fat distribution, so it can misjudge bodybuilders, pregnant women, and people with unusual proportions. For a precise clinical figure, methods like DEXA scanning, hydrostatic weighing, or the Bod Pod are the gold standard. This calculator is intended for general education and self-tracking only — for medical decisions, weight-management programs, or if you have a health condition, consult a doctor or registered dietitian.