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Body fat calculator

The US Navy method estimates body-fat percentage from your height and a tape measure: the neck and abdomen, or the neck, waist and hips.

Input / Measurements

Your details

Units
Equation

Just below the larynx (Adam’s apple).

Optional. Adds fat mass and lean mass.

Use a flexible tape, snug on the skin without pressing in.

Result / Body fat

Result

No input

Choose the male or female equation and enter your measurements to see your body-fat estimate.

How it is calculated

Hodgdon and Beckett fitted these equations for the US Navy in 1984, against underwater weighing in 602 men and 214 women. The US Army prints the same equations in AR 600-9 (2019), Appendix B. This calculator computes them as Pendum Body does.

Every measurement is converted to inches (cm ÷ 2.54) and the logarithms are base 10. The male equation uses the abdomen at the navel; the female equation uses the natural waist and the hips.

Male
%BF = 86.010 × log10(abdomen − neck)
    − 70.041 × log10(height) + 36.76

Female
%BF = 163.205
    × log10(waist + hips − neck)
    − 97.684 × log10(height) − 78.387

Where to measure

Height
Without shoes.
Neck (men and women)
Just below the larynx (Adam’s apple).
Abdomen (men)
Around the abdomen at the navel, at the end of a relaxed breath out.
Waist (women)
At the natural waist, the narrowest point of the abdomen.
Hips (women)
At the widest point of the buttocks, feet together.

Tape level and snug, not pressing into the skin. Measure the same sites the same way each time: tape position moves the result more than anything else.

As in Pendum Body, a result is kept only when it falls between 0 and 75%. Measurements that give anything else, or a circumference term of zero or less (an abdomen no larger than the neck), give no estimate. With a weight, fat mass is weight × body fat % ÷ 100 and lean mass is the rest.

The result is rounded to one decimal and placed in the ACE body-fat categories, with the edges Pendum Body uses.

ACE body-fat categories

ACE body-fat categories for men and women, in percent body fat, with the edges Pendum Body uses
CategoryMenWomen
Very low< 6.0%< 14.0%
Lean6.0–13.9%14.0–20.9%
Typical14.0–24.9%21.0–31.9%
Elevated≥ 25.0%≥ 32.0%

Percent body fat on the one-decimal value. Very low covers ACE’s essential fat range (2 to 5% for men, 10 to 13% for women) and anything below it; the result says which. Lean is ACE’s athlete range, typical its fitness and average ranges together, and elevated its obese range. General comparisons, not personal targets.

The category follows the one-decimal value, so the number and its word always agree. Pendum Body applies the same edges to the unrounded value, so for a result less than 0.05 below an edge (24.96% for a man, shown as 25.0%) the app names the category below the one shown here.

The standard error of the estimate is 3 to 4 percentage points of body fat, so read one result as a range. Tape position moves the result more than anything else: measure the same sites the same way each time and compare your own readings with each other.

For adults. This is an estimate from a tape measure, not a measurement of body fat and not a diagnosis. Small changes in where the tape sits change the result.

Sources

  1. Hodgdon JA, Beckett MB. Prediction of percent body fat for U.S. Navy men from body circumferences and height. Naval Health Research Center, Report 84-11, 1984. DTIC ADA143890.
  2. Hodgdon JA, Beckett MB. Prediction of percent body fat for U.S. Navy women from body circumferences and height. Naval Health Research Center, Report 84-29, 1984. DTIC ADA146456.
  3. U.S. Army. AR 600-9, The Army Body Composition Program (2019), Appendix B, Table B-5.
  4. ACE. Anthropometric measurements: when to use this assessment (2014).
  5. Foulis SA, et al. Body composition changes during 8 weeks of military training are not accurately captured by circumference-based assessments. Front Physiol, 2023.

Method and sources checked on by Svindland Software LLC.

Help / Body fat

Common questions

How accurate is the US Navy body fat method?

The standard error of the estimate is 3 to 4 percentage points of body fat, so read one result as a range. Tape position moves the result more than anything else: measure the same sites the same way each time and compare your own readings with each other.

Where do I measure?

Men: the neck and the abdomen at the navel. Women: the neck, the natural waist and the hips. Every measurement is converted to inches before the equations run, and a result is kept only when it falls between 0 and 75%.

What do the body fat categories mean?

They are the ACE body-fat categories with the edges Pendum Body uses. For men: very low below 6%, lean from 6.0 to 13.9%, typical from 14.0 to 24.9% and elevated from 25.0%. For women: very low below 14%, lean from 14.0 to 20.9%, typical from 21.0 to 31.9% and elevated from 32.0%. These are general comparisons, not personal targets.

Where do the US Navy equations come from?

Hodgdon and Beckett fitted them for the US Navy in 1984, against underwater weighing in 602 men and 214 women. The US Army prints the same equations in AR 600-9 (2019), Appendix B, and this calculator computes them as Pendum Body does.

Is this a measurement of body fat?

No. It is an estimate from a tape measure for adults, not a measurement of body fat and not a diagnosis. Small changes in where the tape sits change the result.

Track / Offline

Pendum Body tracks it over time

One-time purchase, $9.99 once. No account.

Pendum Body makes the same estimate from your tape sites, with a measured percentage taking precedence, and shows it on its dashboard with the adult reference label.

See Pendum Body

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