Body Fat Calculator

How the US Navy Method Works

The US Navy circumference method estimates body fat from tape measurements rather than from weight alone. For men it uses neck and waist circumference plus height; for women it also uses hip circumference. The formula is a logarithmic equation fitted to underwater weighing data collected by the Naval Health Research Center, and it typically lands within a few percentage points of laboratory methods for most people.

The method is popular because it needs only a tape measure, costs nothing, and tracks change over time reasonably well. Its accuracy depends heavily on consistent measurement technique: measure at the same point each time, keep the tape level and snug without compressing the skin, and measure in the morning before eating where possible.

Body Fat Categories

Categories below follow commonly cited ranges from the American Council on Exercise. They are descriptive, not diagnostic.

• Men: Essential 2–5% · Athletic 6–13% · Fitness 14–17% · Average 18–24% · Obese 25%+
• Women: Essential 10–13% · Athletic 14–20% · Fitness 21–24% · Average 25–31% · Obese 32%+

Women carry more essential fat than men because of reproductive and hormonal tissue. This is normal physiology, not a difference in fitness.

Why Body Fat Matters More Than Weight

Body weight tells you how heavy you are but nothing about composition. Two people of identical height and weight can have very different body fat percentages, and therefore different health profiles. Muscle is denser than fat, so a person who gains muscle while losing fat may see no change on the scale while their body composition improves substantially.

Body fat percentage is also more informative than BMI for people with above-average muscle mass, who are frequently misclassified as overweight by BMI alone. That said, circumference formulas have their own limits: they tend to overestimate body fat in very muscular people and can be less accurate at the extremes of the range.