Body fat calculator

How much of your body is fat?

An estimate of your body fat percentage from a tape measure: height, neck and waist, plus the hip for women, by the US Navy method.

Sex

Units

Height

Weight

Neck (cm)

Waist (cm)

Hip (cm)

How to measure

Neck: just below the Adam's apple, the tape sloping slightly down to the front.
Waist: at its narrowest point, after breathing out normally.
Hip: at the widest point of the buttocks.

Estimated body fat

27.2%

About 16.3 kg of your weight is fat.

The rest of your weight

Lean mass (everything but fat): 43.7 kg

Limits of a tape-measure estimate

It is an estimate from tape measurements, not a lab measurement. A scan or a skinfold test by a professional can differ by several percentage points.
Small measuring errors matter: measure on bare skin, keep the tape level and snug, and take each measure twice.
Made for adults. Not for children, in pregnancy, or for very muscular or very lean people, for whom it can be far off.

An estimate of your body fat percentage from a tape measure: height, neck and waist, plus the hip for women, by the US Navy method.

How to use

Choose your sex and whether you measure in centimetres and kilograms or in inches and pounds.
Enter your height and weight.
Measure your neck and waist (women also the hip) with a soft tape and enter them.
Read your estimated body fat percentage and your lean mass.

How it works

Fat is stored more around the waist and hips than around the neck, so the difference between those circumferences, compared with your height, says a lot about how much of your body is fat. The US Navy turned that idea into two equations that only need a tape measure.

For men, body fat % = 86.010 × log10(waist − neck) − 70.041 × log10(height) + 36.76; for women, body fat % = 163.205 × log10(waist + hip − neck) − 97.684 × log10(height) − 78.387, with every measure in inches. For example, a woman 165 cm tall with a 33 cm neck, a 75 cm waist and 95 cm hips gets about 27 %. The equations come from Hodgdon and Beckett at the Naval Health Research Center (1984), who fitted them to underwater-weighing measurements of navy personnel; the US armed forces use them in their body composition programme.

Your fat mass is your weight times that percentage; the rest is lean mass: muscle, bone, organs and water. The result is an estimate. It is less reliable for very muscular or very lean people, and it does not measure where the fat is or what it means for your health.

Worked example

What fat mass does the estimate give for a man weighing 80 kg?

With height 180 cm, waist 90 cm and neck 40 cm, the circumference equation estimates 18.5% body fat.

Estimated fat mass: 80 × 18.5% = 14.8 kg.

Frequently asked questions

Where exactly should I measure?

The neck just below the Adam's apple, with the tape sloping slightly down to the front. Men measure the waist at the navel, women at its narrowest point; women measure the hips at the widest point of the buttocks. Stand relaxed, breathe out normally and keep the tape level and snug on bare skin.

Why does my result differ from my smart scale?

Scales estimate body fat from an electric current through your body, which changes with how much water you have drunk. Tape measures and scales use different methods, so a few percentage points of difference are normal. Comparing the same method over time tells you more.

Why do women also measure the hips?

Women typically store more fat around the hips and thighs, so the women's equation adds the hip to the waist. The men's equation uses only the waist and the neck.

Is lean mass the same as muscle mass?

No. Lean mass includes muscle, bone, organs and water. The calculator does not estimate muscle mass separately.

Why does a small tape-measure change affect the result?

The estimate depends on differences between circumferences. Measure in the same places each time and avoid pulling the tape tighter to change the reading.

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