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BODY FAT / U.S. NAVY METHOD

Body fat calculator (U.S. Navy method)

Estimate your body fat percentage from a tape measure: neck, waist (and hips for women) and height, using the U.S. Navy circumference equations.

Last verified: Methodology

Your details

01You

Units
Sex

The Navy equations are different for men and women.

02Measurements

Directly below the larynx (Adam's apple).

Men: around the abdomen at the navel. Women: at the narrowest point.

Women only: around the widest part of the buttocks.

Estimated body fat

17.5%

U.S. NAVY CIRCUMFERENCE METHOD

Fat mass
Add weight to see
Lean mass
Add weight to see
Circumference value used
19 in (abdomen − neck)
  • The equations have a reported standard error of about 3–4 body-fat percentage points, and tend to underestimate high body fat and overestimate low body fat (Front Physiol 2023), so treat the result as a range. Measure on bare skin with a non-stretch tape.
  • Military services set their own current body composition procedures and standards; this page uses the 1984 Hodgdon & Beckett equations for general estimates only.
  • This is an estimate for general information, not medical advice. Talk to a doctor or other qualified health professional about your own situation.

Estimated body fat: 17.5% U.S. NAVY CIRCUMFERENCE METHOD

How your estimate was worked out

Men: %BF = 86.01 × log10(abdomen − neck) − 70.041 × log10(height) + 36.76, all in inches. Metric measurements are divided by 2.54 first.

StepValue
Height (in)70 in
Abdomen − neck19 in
86.01 × log10(19 in)109.986
70.041 × log10(70 in)129.233
Constant36.76
Estimated body fat17.5%

17.5%

U.S. NAVY CIRCUMFERENCE METHOD

How it's calculated

The U.S. Navy circumference method estimates body fat from a few tape-measure readings and your height. The equations were published by Hodgdon and Beckett of the Naval Health Research Center in 1984 (reports 84-11 for men and 84-29 for women), from measurements of Navy personnel. The same equations appear in Department of Defense Instruction 1308.3 and have been used by the Army, Navy and Marine Corps,Int J Exerc Sci and they are still used in body composition research.Frontiers in Physiology

Measurements:

  • Men: neck (directly below the larynx) and abdomen at the level of the navel.
  • Women: neck, waist at the narrowest part of the torso, and hips at the widest part of the buttocks.

This is an estimate for general information, not medical advice.

The formula

All measurements in inches (metric measurements are divided by 2.54 first):

  • Men: % body fat = 86.010 × log₁₀(abdomen − neck) − 70.041 × log₁₀(height) + 36.76
  • Women: % body fat = 163.205 × log₁₀(waist + hip − neck) − 97.684 × log₁₀(height) − 78.387

If you add your weight, fat mass = weight × body fat %, and lean mass = weight − fat mass.

Worked example

A man 5 ft 10 in tall with a 15 in neck and a 34 in abdomen: 86.010 × log₁₀(19) − 70.041 × log₁₀(70) + 36.76 gives 17.5% body fat.

A woman 5 ft 4 in tall with a 13 in neck, 28 in waist and 38 in hips comes out at 26.6%.

Man, 183 cm, neck 40 cm, abdomen 92 cmBODY FAT / U.S. NAVY METHOD

Estimated body fat: 19.4% U.S. NAVY CIRCUMFERENCE METHOD

Assumptions and limitations

  • An estimate with a wide margin. The equations have a reported standard error of about 3–4 percentage points of body fat. Researchers have found they tend to underestimate body fat at the high end and overestimate it at the low end compared with laboratory methods.Frontiers in Physiology
  • Measure carefully. Small tape errors change the result. Measure on bare skin with a non-stretch tape, and repeat the reading to check it.
  • No health categories. We have not found an agency classification of body fat percentages for the general public that we can cite, so the page reports the number only. Military services set their own standards and current procedures, which can differ from these 1984 equations.
  • Adults. The equations come from adult Navy personnel; they were not developed for children or for pregnancy.

BMI is the other common screening measure; see the BMI calculator and our guide to BMI, calories and macros.

FAQ

Questions people ask

How does the U.S. Navy body fat method work?

It estimates body fat percentage from your height and a few circumference measurements, using equations Hodgdon and Beckett published at the Naval Health Research Center in 1984. Men measure the neck and abdomen at the navel; women measure the neck, the narrowest part of the waist and the widest part of the hips. The calculator applies the published log equations.

Where exactly should I measure?

Measure the neck directly below the larynx, or Adam's apple. Men measure the abdomen at the level of the navel. Women measure the waist at the narrowest part of the torso and the hips at the widest part of the buttocks. Use a non-stretch tape on bare skin and repeat each reading to make sure it is consistent.

How accurate is the tape measure method?

It is an estimate. Studies report a standard error of about 3 to 4 percentage points of body fat, and researchers have found the equations tend to underestimate high body fat and overestimate low body fat compared with laboratory methods such as DXA scans. Use the result to track change over time with the same measuring technique rather than as an exact figure.

Can I enter measurements in centimeters?

Yes. Switch the units to metric and enter centimeters. The equations were written for inches, so the calculator divides each measurement by 2.54 before applying them, which gives the same answer as measuring in inches. Height can be entered in centimeters too.

What is a healthy body fat percentage?

We have not found a health agency classification of body fat percentage for the general public that we can cite, so the calculator reports the number without a category. Military services set their own standards for service members. For a general screening category, CDC uses BMI; ask a health care provider how to interpret your body fat result.

Why do I need my weight?

You don't need it for the percentage itself, which depends only on your height and circumferences. If you add your weight in the optional field, the calculator multiplies it by your estimated body fat percentage to show fat mass, and subtracts that from your weight to show lean mass, in pounds or kilograms.

Sources

  1. Naval Health Research Center (DTIC)Hodgdon JA, Beckett MB. Prediction of percent body fat for U.S. Navy men from body circumferences and height (NHRC Report 84-11, 1984) · retrieved 2026-10-17
  2. Naval Health Research Center (DTIC)Hodgdon JA, Beckett MB. Prediction of percent body fat for U.S. Navy women from body circumferences and height (NHRC Report 84-29, 1984) · retrieved 2026-10-17
  3. Frontiers in PhysiologyBody composition changes during 8 weeks of military training are not accurately captured by circumference-based assessments (Front Physiol 2023), methods: Hodgdon & Beckett equations · retrieved 2026-10-16
  4. Frontiers in PhysiologyCircumference-Based Predictions of Body Fat Revisited: Preliminary Results From a US Marine Corps Body Composition Survey (Front Physiol 2022) · retrieved 2026-10-16

Last verified: CalcBloc Editorial Team