Body fat calculator
This uses the US Navy circumference method, which estimates body fat from tape measurements rather than a scale. Measure at the narrowest part of the neck and, for the waist, at the navel.
Result
- Estimated body fat
- 12.3%
- Category
- Athletes
- Method
- US Navy (male)
Worked examples
US Navy method, male
Height 178 cm, neck 38 cm, waist 88 cm.
- convert to inches: 70.1, 15.0, 34.6
- waist − neck = 19.6
- apply the Navy formula
About 12.3% body fat.
How the circumference method works
The US Navy method estimates body fat from tape measurements rather than from weight. It works because fat distributes in reasonably predictable places, so the ratio between waist, neck and height correlates with overall body composition across a population.
Men need neck, waist and height. Women need hip as well, because female fat distribution makes the waist measurement alone a weaker predictor.
Measuring consistently matters more than measuring perfectly
Measure the neck at its narrowest point, just below the larynx, and the waist at the navel for men or at the narrowest point for women. Keep the tape level and snug without compressing the skin.
Small errors matter: a centimetre at the waist can shift the estimate by roughly a percentage point. Since the useful information is the trend over weeks, measure the same way, at the same time of day, each time.
What the number is and is not
This is a population-level estimate, not a measurement of your body. Against DEXA — the usual reference standard — circumference methods typically sit within a few percentage points for most people, and drift further at the extremes of very lean or very heavy.
It is also silent on where fat sits, and visceral fat around the organs carries different health implications from subcutaneous fat. Treat the figure as one input among several.
Formula
Men: 495 ÷ (1.0324 − 0.19077 × log₁₀(waist − neck) + 0.15456 × log₁₀(height)) − 450
Worth knowing
- Measurements are converted to inches internally, which is what the original formula expects.
- This is an estimate from tape measurements. It is not a substitute for DEXA or hydrostatic weighing, and it is least accurate at the extremes.
Frequently asked questions
How accurate is the US Navy body fat method?
It is typically within a few percentage points of DEXA for people in the middle of the range, and less reliable for very lean or very heavy individuals. It is best used to track change over time rather than as an absolute figure.
Where exactly should I measure?
Neck at its narrowest point just below the larynx. Waist at the navel for men, at the narrowest point for women. Hips at the widest point. Keep the tape level and snug but not tight.
Why do women need a hip measurement?
Female fat distribution means the waist alone predicts total body fat less reliably, so the formula includes hip circumference to compensate.
What is a healthy body fat percentage?
Commonly cited ranges are roughly 8–19% for men and 21–32% for women, varying with age and source. Athletes are often below these, which is not necessarily unhealthy.
Is body fat percentage better than BMI?
For body composition, generally yes — BMI cannot distinguish muscle from fat, so it misclassifies muscular people as overweight. Neither tells you where fat is stored.