# Body Fat Calculator (Navy Method)

URL: https://speedycalculator.com/calculators/health/body-fat/
Last updated: 2026-10-25

> This body fat calculator estimates body fat percentage from height and tape measurements of the neck, waist and, for women, hips using the U.S. Navy circumference method. It needs only a measuring tape and is usually within a few percentage points of laboratory methods.

## Inputs

- Sex
- Height (cm, m, in, ft)
- Neck circumference (cm, m, in, ft) — Measure just below the larynx, tape sloping slightly down to the front.
- Waist circumference (cm, m, in, ft) — Men: at the navel. Women: at the narrowest point.
- Hip circumference (women) (cm, m, in, ft) — Widest point of the buttocks. Ignored for men.

## Results

- Body fat

## Formula

```
Men: %BF = 86.010·log10(waist − neck) − 70.041·log10(height) + 36.76
Women: %BF = 163.205·log10(waist + hip − neck) − 97.684·log10(height) − 78.387
(all measurements in inches)
```

## Explanation

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

FieldWhat to enterSexChoose one: Male, FemaleHeightUnits: cm, m, in, ftNeck circumferenceUnits: cm, m, in, ft. Measure just below the larynx, tape sloping slightly down to the front.Waist circumferenceUnits: 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.

## 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.

## FAQ

**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