How this calculator works
The 2002 DoD instruction prints separate equations for men and women and credits the Hodgdon-Beckett research. Choose the equation and enter positive measurements in any offered units. The calculator converts lengths to inches. Tape placement affects the estimate: use the navel for men, the natural waist and hips for women, and the neck for both. This tool evaluates the entered numbers without applying the historical repeated-measurement and half-inch recording procedure. The decimal result is before official whole-percent rounding and does not imply measurement accuracy. The source has estimation tables, but no body-fat category table. Its service standard limits are not health categories. The result is an estimate for information only and is not medical advice.
Formula
All lengths below are in inches; log10 is the base-10 logarithm. Men: %BF = 86.010 x log10(abdomen - neck) - 70.041 x log10(height) + 36.76. Women: %BF = 163.205 x log10(waist + hip - neck) - 97.684 x log10(height) - 78.387. The logarithm requires abdomen > neck for men, or waist + hip > neck for women.
Worked example
For a man with height 70 in, abdomen 36 in and neck 15 in, the difference is 21 in. The equation gives 86.010 x 1.322219295 - 70.041 x 1.845098040 + 36.76 = 21.25157%, displayed as 21.3%. The same measurements are 177.8 cm, 91.44 cm and 38.1 cm.
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Frequently asked questions
Where should I place the tape?
Use a level tape at the navel for the male abdomen, at the narrowest abdominal point for the female waist, and around the widest part of the buttocks for hips. Measure the neck just below the larynx. Keep the tape snug without compressing bare skin.
Can I mix centimetres and inches?
Yes. Each measurement has its own unit selector. The engine converts each entry before the equation runs. Enter decimal feet when selecting feet: 5 ft 6 in is 5.5 ft.
Why is there only one method?
DoDI 1308.03, issued in 2022, replaced the 2002 instruction and allowed several assessment approaches. It did not publish the requested one-site equations using weight and abdomen circumference, so this page offers only the verified 2002 equations.
Does this result decide whether I meet Navy standards?
No. This is a historical equation estimate. It does not apply current service rules, official measurement recording or eligibility decisions. The displayed decimal also carries no fitness category.
Sources
- DoDI 1308.3, DoD Physical Fitness and Body Fat Programs Procedures (5 November 2002), Enclosure 3, p. 13, E3.1.2-E3.1.3: inches, rounding and both equations (archived official PDF)
- DoDI 1308.3 (2002), pp. 14-17, E3.1.4-E3.1.7: measurement procedure and Hodgdon-Beckett reports 84-11 and 84-29; p. 7, 6.2.2.4: service standard limits
- DoDI 1308.03, DoD Physical Fitness/Body Composition Program (10 March 2022), p. 1: supersession; p. 9, 3.2.f.(2): permitted assessment methods, without replacement equations (archived official PDF)