The circumference method was developed for the U.S. Navy as a practical field test. It links the ratio of abdominal to neck girth with body fat measured by underwater weighing.
How to measure
- Neck: just below the larynx, tape sloping slightly down at the front.
- Waist: men at the navel; women at the narrowest point.
- Hips (women): around the widest part of the buttocks.
Measure on bare skin, relaxed, after breathing out normally. Take each measurement twice and use the average.
Typical ranges
Essential fat is about 2–5% for men and 10–13% for women. Many guidelines consider roughly 10–20% for men and 20–30% for women a healthy range for adults, varying with age.
Accuracy
Expect an error of about ±3–4 percentage points. Use the same technique each time to track changes reliably.
Inputs explained
| Field | What to enter |
|---|---|
| Sex | Choose one: Male, Female |
| Height | Units: cm, m, in, ft |
| Neck circumference | Units: cm, m, in, ft. Measure just below the larynx, tape sloping slightly down to the front. |
| Waist circumference | Units: cm, m, in, ft. Men: at the navel. Women: at the narrowest point. |
| Hip circumference (women) | Units: cm, m, in, ft. Widest point of the buttocks. Ignored for men. |
Formula
Men: %BF = 86.010·log10(waist − neck) − 70.041·log10(height) + 36.76Women: %BF = 163.205·log10(waist + hip − neck) − 97.684·log10(height) − 78.387(all measurements in inches)Worked example
Man, height 178 cm (70.08 in), neck 38 cm (14.96 in), waist 86 cm (33.86 in).
%BF = 86.010 × log10(18.90) − 70.041 × log10(70.08) + 36.76
≈ 86.010 × 1.2765 − 70.041 × 1.8456 + 36.76 ≈ 17.3%.
Key terms
- Body fat percentage
- Fat mass divided by total body mass.
- Essential fat
- The minimum fat needed for normal physiological function.
- Circumference method
- Estimating body composition from tape measurements.
Frequently asked questions
Is the Navy method accurate?
It is reasonably accurate for most adults, typically within 3–4 percentage points of lab methods.
Why do women need a hip measurement?
Women store more fat around the hips, so the equation includes it for better accuracy.
Can I use centimetres?
Yes. Enter any unit; the calculator converts to inches internally.
What formula does the Body Fat Calculator use?
Men: %BF = 86.010·log10(waist − neck) − 70.041·log10(height) + 36.76.
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, 1984