Body Fat Calculator

Based on peer-reviewed medical formulas. See our formulas & sources →

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Tape-Measure vs DEXA: The Real Accuracy

A DEXA scan — the gold standard for body composition — uses X-rays to measure fat and lean mass precisely, but it costs money and takes a machine. The U.S. Navy method behind this calculator instead estimates body fat percentage from just a tape measure around your neck, waist, and (for women) hips, plus your height. It won't match DEXA to the decimal, but research places it within about 3-4% — close enough to reliably track changes over time without leaving your home.

Body fat serves essential functions: it protects your organs, insulates your body to maintain temperature, stores energy for future use, and produces important hormones. However, too much body fat — particularly visceral fat stored around your organs — is associated with increased risks of heart disease, type 2 diabetes, and other metabolic conditions. Too little body fat can also be problematic, as it may lead to hormonal imbalances, weakened immune function, and nutrient deficiencies.

The US Navy method used in this calculator estimates body fat by measuring the circumference of your neck, waist, and (for women) hips, along with your height. Research shows this method is accurate to within 3-4% of DEXA scans, which are considered the gold standard for body composition measurement. While not perfect, it provides a practical and accessible way to track changes in your body composition over time without expensive equipment.

Understanding your body fat percentage helps you set realistic fitness goals and track progress more accurately than the scale alone. For example, you might gain muscle while losing fat, which would show as no change on the scale but a significant improvement in body fat percentage. This is why body fat measurement is preferred by fitness professionals and athletes for assessing true progress.