Your body fat. With a tape measure.

How it is calculated

1. Men: body fat % = 495 ÷ (1.0324 − 0.19077 × log(waist − neck) + 0.15456 × log(height)) − 450.
2. Women: body fat % = 495 ÷ (1.29579 − 0.35004 × log(waist + hips − neck) + 0.221 × log(height)) − 450. All measurements in cm, log is the base-10 logarithm.
3. How to measure: tape level and not too tight, ideally in the morning. Men measure the waist at the navel, women at the narrowest point and the hips at the widest, the neck just below the larynx.
4. Rating by Gallagher and colleagues (2000): body fat percentages that correspond to a BMI of 18.5, 25 and 30 in adults – by age and sex.

What the value does not show

• The Navy method estimates from girths. Individual results can be a few percentage points off; DXA scans, for example, measure more precisely.
• A single centimetre at the waist changes the result noticeably. Always measure the same way and compare the trend.
• The ranges were derived for adults aged 20 to 79 of European origin; for other groups the values partly differ.
• The method fits poorly for very muscular people and in pregnancy.

Sources

1. Hodgdon JA, Beckett MB (1984): Prediction of percent body fat for U.S. Navy men and women from body circumferences and height. Naval Health Research Center, San Diego, Reports 84-11 and 84-29.
2. Gallagher D, Heymsfield SB, Heo M et al. (2000): Healthy percentage body fat ranges: an approach for developing guidelines based on body mass index. American Journal of Clinical Nutrition 72(3).