Body fat calculator
Estimate your body fat percentage with a tape measure using the U.S. Navy circumference method: height, neck and waist, plus hips for women. Also shows fat mass and lean mass.
The Navy equations
Developed for the U.S. Navy in the 1980s, these equations estimate body fat from a few circumferences and height. They need only a flexible tape, which makes them one of the most practical ways to follow body composition at home.
women: %BF = 495 ÷ (1.29579 − 0.35004·log10(waist + hip − neck) + 0.22100·log10(height)) − 450
(all in cm)
Why track body fat at all
The scale cannot tell fat from muscle or water. If you are strength training while eating in a deficit, your weight may stall while your waist shrinks. A tape measure (or a phone-based body scan) shows that progress when the scale does not. Pair it with your BMR: with a body-fat estimate, the Katch-McArdle equation can personalize your energy needs.
Questions
How accurate is the Navy body fat method?
It is a reasonable field estimate. Compared with lab methods, tape-measure equations are typically within a few percentage points for many people, but errors grow at the extremes of body shape. Measure the same way each time and watch the trend.
Where do I measure my waist and neck?
Measure the neck just below the larynx, the waist at the navel (for men) or at the narrowest point (commonly used for women), and the hips at the widest point. Keep the tape level and snug without compressing the skin, and measure relaxed, not sucking in.
What is a healthy body fat percentage?
Ranges vary by source, age and sex. Many references describe roughly 10–20% for men and 18–30% for women as typical healthy ranges for adults.
How often should I measure body fat?
Every two to four weeks is enough. Day-to-day changes are mostly water and measurement noise.
Sources
- Hodgdon JA, Beckett MB. Prediction of percent body fat for U.S. Navy men and women from body circumferences and height. Naval Health Research Center Reports 84-11 and 84-29; 1984.
- U.S. Department of Defense. DoD Instruction 1308.03, DoD Physical Fitness and Body Fat Programs (circumference method).
Built and checked by Ingrid Solberg. Last reviewed October 22, 2026. All formulas: formulas & sources.