How to estimate body fat with a tape measure

Steps

1. Measure your height, neck (below the larynx) and waist (at the navel) in centimetres. Women also measure the hips at the widest point.
2. Use a soft tape, keep it level and snug without squeezing, and breathe out normally.
3. Enter the measurements and your weight in the body fat calculator.
4. Read the body fat percentage, the fat mass and the lean mass.
5. Measure again under the same conditions every few weeks to see the trend.

The formulas

For men: body fat % = 495 ÷ (1.0324 − 0.19077 × log10(waist − neck) + 0.15456 × log10(height)) − 450. For women the waist, hips and neck are combined: 495 ÷ (1.29579 − 0.35004 × log10(waist + hip − neck) + 0.22100 × log10(height)) − 450. All lengths are in centimetres.

For the man above the waist minus neck is 47 cm, which gives about 16.9%, so 11.9 kg of fat and 58.1 kg of lean mass. A woman at 162 cm and 62 kg, with a neck of 32 cm, a waist of 76 cm and hips of 98 cm, comes out at about 30% body fat, or 18.8 kg of fat and 43.2 kg of lean mass.

How accurate is it

A tape estimate can be several percentage points off, because it infers body fat from a few circumferences. It is best used to follow your own trend, since measuring the same way each time cancels much of the error. Scans in a clinic or lab are more accurate but not available for everyday use.

What the number means

Healthy ranges differ by age and sex, and women naturally carry more essential fat than men. Rather than aim at a target figure from a table, look at whether the waist is shrinking and the weight, strength and energy are going the right way. This page gives general information, not medical advice.