The tape-measure test was designed for a practical problem: the US Navy needed a way to check body composition for thousands of sailors without laboratory equipment. In the early 1980s Hodgdon and Beckett at the Naval Health Research Center fitted equations that predict body fat from a few circumferences and height, using underwater weighing as the reference. The method has been used in the armed forces ever since and is now widely used by civilians because all it takes is a tape.
This calculator applies those equations, converts the result into fat and lean mass, and compares it with the Navy’s maximum body fat for your age and sex. It is a screening estimate and is not a medical assessment.
How to use the Navy body fat calculator
- Select your sex and enter your age. The Navy limit depends on both.
- Enter height and weight. Height is without shoes.
- Measure your neck just below the larynx, sloping slightly downward at the front.
- Measure your waist. Men measure at the navel; women at the narrowest point of the torso. Women also measure the hips at the widest point.
- Read the body fat estimate and the comparison with the Navy standard.
Navy body fat formula
Women: %BF = 163.205 × log10(waist + hip − neck) − 97.684 × log10(height) − 78.387
(all lengths in inches)
The equations are from Hodgdon JA and Beckett MB, Naval Health Research Center reports 84-29 and 84-11 (1984), and are given in the US Department of Defense body-composition procedures (DoD Instruction 1308.3). Fat mass is weight × %BF ÷ 100; lean mass is the rest.
Worked example
A 30-year-old man, 70 in tall, 180 lb, neck 15.5 in, waist 34 in.
- Waist − neck = 34 − 15.5 = 18.5 in; log10(18.5) = 1.2672
- log10(70) = 1.8451
- %BF = 86.010 × 1.2672 − 70.041 × 1.8451 + 36.76 = 16.5%
- Fat mass = 180 × 16.5% = 29.7 lb; lean mass = 150.3 lb
- The Navy maximum for men aged 17–39 is 22%, so this result is within the standard.
Navy maximum body fat standards
| Group | Age | Maximum body fat (Navy standard) |
|---|---|---|
| Men | 17–39 | 22% |
| Men | 40 and over | 23% |
| Women | 17–39 | 33% |
| Women | 40 and over | 34% |
These limits are the standards in OPNAVINST 6110.1J (2016). The Navy revises its policy from time to time, and for service members the instruction in force, not this page, applies.
How waist and height change the result for men
Estimated body fat for a man with a 15.5 in neck.
| Waist (neck 15.5 in) | Height 66 in | Height 70 in | Height 74 in |
|---|---|---|---|
| 30 in (76 cm) | 9.2% | 7.4% | 5.7% |
| 32 in (81 cm) | 14.0% | 12.2% | 10.6% |
| 34 in (86 cm) | 18.3% | 16.5% | 14.8% |
| 36 in (91 cm) | 22.1% | 20.4% | 18.7% |
| 38 in (97 cm) | 25.6% | 23.8% | 22.1% |
| 40 in (102 cm) | 28.8% | 27.0% | 25.3% |
Getting a reliable reading
- Be consistent. Use the same tape, time of day and posture each time.
- Breathe out normally. Do not suck in your stomach or flex.
- Round to the nearest half inch, as in Navy practice, and average two or three readings.
- Know the margin. The waist enters the equation as a logarithm, but a 1 in error still moves the estimate by roughly 1.5 to 2 percentage points.
If you do not want to take tape measurements, the Body Fat Calculator also offers a BMI-based estimate. To see the muscle-and-organ side of the picture use the Lean Body Mass Calculator, and for a ratio-based screen of abdominal fat try the Waist-to-Height Ratio Calculator. For Army rules, see the army-body-fat-calculator.
This page is for information only and is not medical or dietary advice. Speak to a doctor or registered dietitian before making large changes to your diet or exercise.
Sources
- 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.
- 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.
- US Department of Defense Instruction 1308.3, Physical Fitness/Body Composition Program Procedures.
- US Navy. OPNAVINST 6110.1J, Physical Readiness Program, 2016 (body composition standards).
Frequently asked questions
How does the Navy body fat method work?
It estimates body fat from height, neck and waist circumference for men, plus hip circumference for women, using logarithmic equations fitted by Hodgdon and Beckett to underwater-weighing data from Navy personnel. The idea is that a thick waist relative to neck and height signals more abdominal fat.
How should I take the measurements?
Stand relaxed. Measure the neck just below the larynx, the waist at the navel for men and at the narrowest point for women, and the hips at the widest point. Keep the tape level and snug without compressing the skin, and round to the nearest half inch. Take each twice and average.
What body fat does the Navy allow?
Under OPNAVINST 6110.1J (2016) the maximum body fat is 22 percent for men aged 17–39 and 23 percent at 40 and over, and 33 and 34 percent for women. Policies change, so check the current instruction if your career depends on it.
How accurate is it?
For groups it tracks laboratory methods fairly well, but for an individual the error is often 3 to 4 percentage points. It tends to be less reliable for very lean, very muscular or very large people. Use the same method over time to follow trends.
Is this the same as the Army tape test?
The Army uses its own tables and rules, which are changing; see the army-body-fat-calculator. The Navy method here follows the original Hodgdon and Beckett equations.