Calculator
Body Fat Calculator
Estimate body fat percentage using the U.S. Navy circumference method.
What is the U.S. Navy body fat method?
It’s a body fat percentage estimate developed by the U.S. Navy as a fast, no-equipment alternative to underwater weighing. Instead of measuring fat directly, it uses the relationship between waist/neck circumference (and hip, for women) and body fat percentage to estimate a number from a tape measure alone.
Frequently asked questions
How is body fat percentage calculated here?
The formula uses the log of your waist and neck circumference (plus hip for women) relative to your height. Broadly, a larger waist relative to neck and height pushes the estimate up, since abdominal circumference correlates reasonably well with body fat in most people.
What is a healthy body fat percentage?
For men, roughly 10-20% is considered a fit-to-average range depending on age; for women, roughly 18-28%, since women naturally carry more essential fat. Athletes often sit below these ranges, and both ranges rise somewhat with age.
Why does the calculator ask for hip measurement only for women?
The U.S. Navy formula uses different equations for men and women because fat distribution differs by sex on average. The women's equation adds hip circumference because it improves accuracy for typical female fat distribution patterns; the men's equation doesn't need it.
How accurate is this compared to DEXA or hydrostatic weighing?
Less accurate in absolute terms — circumference methods typically have a margin of error of a few percentage points versus lab methods like DEXA scans or hydrostatic (underwater) weighing. It's most useful for tracking your own trend over time with a consistent measuring technique, not for a precise one-time number.
The U.S. Navy method is an estimate based on body circumferences, not a clinical measurement (like DEXA or hydrostatic weighing). Use it for tracking trends, not diagnosis.