Key Takeaways
- The "Navy body fat formula" is the Department of Defense tape equation. It uses height, neck and waist, plus hips for women[1]. Until 2026 the Navy's last assessment step read a table built from it[4].
- The Navy now uses two steps. Step 1 is waist divided by height, and 0.5499 or lower passes. Step 2 reads a table by height minus waist and weight[6].
- The Navy limits are 26% for men and 36% for women[6]. The June 2026 guide lists no age-adjusted goals. The February 2025 guide did[4].
- The tape equation is an estimate. The 1984 studies reported typical errors of 3.5 points for men and 3.7 for women[3][2]. A 2026 Navy study found it read high for women and low for men against DXA[7].
- Inches and centimetres use different constants. Typing centimetres into the inch equation gives a wrong answer, so this tool converts for you.
The Navy Body Fat Formula
The 2002 DoD instruction gives the equations in inches with base-10 logarithms[1]. Men use the waist at the navel. Women use the natural waist, which is the narrowest part of the abdomen.
| Version | Men | Women |
|---|---|---|
| DoD, inches (this tool) | 86.010 × log10(waist − neck) − 70.041 × log10(height) + 36.76 | 163.205 × log10(waist + hip − neck) − 97.684 × log10(height) − 78.387 |
| NHRC 1984, centimetres | 495 ÷ (1.0324 − 0.19077 × log10(waist − neck) + 0.15456 × log10(height)) − 450 | 495 ÷ (1.29579 − 0.35004 × log10(waist + hip − neck) + 0.22100 × log10(height)) − 450 |
Two sets of constants exist. Use the one that matches your unit.
Both 1984 reports print the equation in centimetres. They predict body density, then convert it to body fat with Siri's formula[3][2]. The 2002 DoD inch equations are a separate set, and I could not trace where their constants came from.
The DoD tables come from the inch equations, rounded to whole percentages. The tool's tests reproduce entries from those tables and from the Navy's February 2025 men's table[4].
The 2002 instruction has since been replaced. The August 2026 DoW instruction does not print a body fat equation[10], so treat this as the historical Navy formula.
Worked example: man, 70 in, neck 15 in, waist 34 in
Waist − neck = 34 − 15 = 19
86.010 × log10(19) = 86.010 × 1.2788 = 110.0
70.041 × log10(70) = 70.041 × 1.8451 = 129.2
Body fat = 110.0 − 129.2 + 36.76
For a woman at 65 in with a 13 in neck, 30 in natural waist and 40 in hips, the same method gives 31.1%. The 1984 equation gives 30.8%.
How to Measure
Use a tape that does not stretch, ideally fiberglass. It should touch the skin without squeezing it and stay parallel to the floor[6].
| Measurement | How | Round |
|---|---|---|
| Height | Shoes off, socks on, standing straight, head level, measured to the highest point of the scalp | Up to ½ in |
| Waist, everyone | Across the belly button on bare skin, feet shoulder width apart, arms down, at the end of a normal breath out | Down to ½ in |
What Navy Guide-4 (June 2026) measures now.
The tape equation needs neck and, for women, a natural waist and hips. The Navy's February 2025 guide describes those sites[4]. It is the last Navy guide that used them.
| Measurement | Where |
|---|---|
| Neck | Just below the Adam's apple, not over it, shoulders down and relaxed |
| Waist, men | Across the navel, arms down, end of a normal breath out |
| Waist, women | Narrowest point of the abdomen, usually about halfway between navel and breastbone |
| Hips, women | Over the greatest protrusion of the buttocks, seen from the side |
Sites for the tape equation, as printed in the February 2025 Navy guide.
Take the waist twice, as the Navy does, and measure each site in turn instead of repeating one site back to back. The Navy takes a third waist reading if the first two differ by more than an inch.
The body fat estimate here uses your raw numbers without rounding. The Step 1 screen rounds the way Guide-4 does.
Navy Body Fat Standards and Limits
Guide-4 (June 2026) sets a maximum of 26% for men and 36% for women[6]. A Sailor above that limit is not within standards. The whole fitness assessment then counts as a failure for the cycle, unless the High-Performance BCA Exemption applies.
These match the ceilings in the Department of War instruction, which does not allow a service limit above 26% for men or 36% for women[10].
The February 2025 guide also had lower age-adjusted goals, from 22 to 26% for men and 33 to 36% for women. Passing Sailors above their goal went into the Fitness Enhancement Program[4]. I could not find them in the June 2026 guide[6], so this page does not use them.
The limits apply to the Navy's own Step 2 figure. A home estimate near the line is not a pass or a fail.
How Accurate Is It?
Each source below looked at something different, so read the last column before you trust a number.
| Source | What it found | Limit |
|---|---|---|
| NHRC 84-11, men[3] | 602 Navy men aged 18 to 56, against underwater weighing: r = 0.90 and a standard error of 3.52 body fat points. In a separate group of 100 men the error was 2.70 points. | 1984 equations. The DoD inch equations are a separate set. |
| NHRC 84-29, women[2] | 214 Navy women aged 18 to 44, against underwater weighing: r = 0.85 and a standard error of 3.72 points. In two other groups of women the errors were 4.04 and 4.36 points. | Same as above. |
| DoDI 1308.3, 2002[1] | Says the method can be applied by Service members with minimal error, plus or minus 1 percent. | No data in the instruction, and far tighter than the studies above, so I do not repeat it as accuracy. |
| McClintock and colleagues, 2021[12] | 102 Sailors against DXA. The tape equation averaged 21.9% for men against 21.6% for DXA, and 36.1% for women against 32.6%. Standard error was 2.1 points for men and 2.3 for women. | Conference abstract, and I read the abstract only. The authors concluded the equations were still accurate. |
| NHRC 26-05, 2026[7] | 757 active duty Sailors against DXA. The Navy circumference method read high in women and low in men. The authors' single-site abdominal equation did not differ from DXA in their sample. | I read the abstract only. That equation was fitted to the same data. Few Sailors under 25 took part, and volunteers may not represent everyone. |
In plain terms, expect an estimate that can be off by a few points either way. In both newer samples the women's tape estimate averaged above the DXA value.
Use the result to track change with the same tape and the same sites, not to settle a fitness standard.
What Is Left Out
I did not reproduce the Step 2 tables. The guide prints them as lookup tables with no equation, and they run to dozens of pages[6]. Use the official Guide-4 for those.
I also left out body fat category charts, because I did not find a primary source I could check for them.
The Army now scores a waist-to-height ratio under 0.55 instead of its old tape test[11]. I did not check the Marine Corps or Air Force rules.
For a ratio without neck or hips, try the waist-to-height ratio calculator.
This tool does not replace an official assessment. A CFL or trained ACFL must do the official one[6].
Frequently Asked Questions
Sources & References
- DoD Instruction 1308.3: DoD Physical Fitness and Body Fat Programs Procedures (2002, since replaced; copy hosted on a third-party site). U.S. Department of Defense (2002)
- Prediction of Percent Body Fat for U.S. Navy Women from Body Circumferences and Height (NHRC Report 84-29). Hodgdon JA, Beckett MB. Naval Health Research Center (1984)
- Prediction of Percent Body Fat for U.S. Navy Men from Body Circumferences and Height (NHRC Report 84-11). Hodgdon JA, Beckett MB. Naval Health Research Center (1984)
- Navy Physical Readiness Program Guide-4: Body Composition Assessment (FEB 2025, superseded by JUN 2026). OPNAV N171, U.S. Navy (2025)
- NAVADMIN 264/25: Navy Physical Readiness Program for Calendar Year 2026 (copy hosted on a third-party site). Chief of Naval Personnel (2025)
- Navy Physical Readiness Program Guide-4: Body Composition Assessment (JUN 2026). OPNAV N171, U.S. Navy (2026)
- Revisiting Navy Body Composition Assessments for Health and Performance (NHRC Technical Report 26-05, abstract read). Cialdella Kam L, Sterringer T, Polan M, Stone M. Naval Health Research Center (2026)
- OPNAVINST 6110.1L CH-1: Physical Readiness Program. Chief of Naval Operations (2025)
- MyNavy HR Physical Readiness Program page (updated 4 November 2026). MyNavy HR, U.S. Navy (2026)
- DoW Instruction 1308.03: DoW Physical Fitness/Body Composition Program (effective 31 August 2026; copy hosted on a third-party site). U.S. Department of War (2026)
- Army Directive 2026-13: Army Body Composition Program and Standards. U.S. Department of the Army (2026)
- Comparison of U.S. Navy's Body Fat Circumference Equation With Dual-Energy X-ray Absorptiometry (conference abstract, abstract read). McClintock RJ, Weller RS, Jones DM, Laird MD, Hodgdon JA, Heaney JH. Medicine & Science in Sports & Exercise (2021)
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Disclaimer: This tool is for informational and personal journaling purposes only. Results are estimates based on published formulas and may vary based on individual factors such as genetics, training history, and measurement technique.