Body Fat Calculator — US Navy method

The US Navy method is a formula that estimates body fat percentage from body circumferences: neck, waist and, for women, hips, combined with height. It was developed to assess body composition quickly without specialist equipment. All you need is a tape measure, so the measurement can be done at home.

Measure the neck just below the larynx, keeping the tape horizontal. Measure the waist at the navel for men and at the narrowest point for women. Measure the hips (women only) at the widest part of the buttocks. Take measurements in the morning, do not hold your breath or pull in your stomach, and keep the tape snug but not tight.

The category code is a numeric label for a body fat range. Code 1 = essential fat (very low), 2 = athlete level, 3 = fitness level, 4 = acceptable level, 5 = obesity. Thresholds differ between sexes because women physiologically carry more body fat than men at the same state of health.

For men: below 6% is essential fat (code 1), 6-13% athlete level (code 2), 14-17% fitness level (code 3), 18-24% acceptable level (code 4), and 25% or more is obesity (code 5). Very low body fat (below 5-6%) is dangerous because essential fat protects internal organs.

For women: below 14% is essential fat (code 1), 14-20% athlete level (code 2), 21-24% fitness level (code 3), 25-31% acceptable level (code 4), and 32% or more is obesity (code 5). Women need a higher minimum fat level (about 10-13%) for normal hormonal balance and reproductive function.

The US Navy formula has two variants. In men fat is stored mainly around the abdomen, so waist and neck are sufficient. In women a significant share of fat accumulates around the hips and thighs, so the formula adds hip circumference to improve accuracy.

The US Navy method has a margin of error of about +/-3-4% compared with reference methods. It is less accurate than DEXA or hydrostatic weighing but far more convenient and cheaper. Its greatest value is tracking change over time: if you measure consistently, it shows the trend well.

BMI is based only on body weight and height and does not distinguish muscle from fat. A muscular person may have a high BMI with low body fat. Body fat percentage directly estimates the share of fat in the body, so it describes body composition and metabolic health better than BMI alone.

No. The result is an estimate only. The US Navy method has a margin of error of +/-3-4% and does not replace precise measurement such as DEXA, hydrostatic weighing or medical bioimpedance. If you have concerns about your body composition or health, consult a physician or dietitian.