US Navy Body Fat Calculator
The US Navy method estimates your body fat percentage with a tape measure instead of calipers, scales, or scans. You enter your height plus a few circumferences (neck and waist for men; neck, waist, and hips for women) and a published equation turns them into an estimate. This calculator runs the equation in your browser, then shows how your result compares with general body fat ranges and, if you add your age, the Navy's own maximum standards. It is for informational and educational use only.
How to take your measurements
Your result is only as good as your measurements, and a small error in the neck or waist moves the answer more than most people expect. A few minutes of care here is worth it.
- Use a flexible, non-stretch tape, such as a cloth or fiberglass tailor's tape. Stretchy tapes and stiff metal tapes both give poor readings.
- Measure against bare skin or very thin clothing, standing relaxed with your weight even on both feet.
- Keep the tape level with the floor all the way around, snug against the skin without pressing into it.
- Measure at the end of a normal exhale. Don't pull your stomach in or flex.
- Take each measurement three times and use the average. If your readings differ by more than about a quarter inch (half a centimeter), measure again.
- If you are tracking change over weeks, measure at the same time of day, such as first thing in the morning.
Height
Stand barefoot with your heels, back, and head against a wall and look straight ahead. Rest a flat object on top of your head, mark the wall, and measure from the floor to the mark.
Neck
Place the tape just below the larynx (Adam's apple), sloping very slightly downward toward the front. Keep your shoulders relaxed and don't flare your neck muscles or hunch forward.
Abdomen (men)
Wrap the tape horizontally around your abdomen at the level of your navel.
Waist (women)
Measure around the narrowest point of your torso, usually above the navel. If there is no obvious narrowing, measure at the navel.
Hips (women)
With your feet together, measure around the widest part of your hips and buttocks.
The Navy body fat formula
The method converts your measurements into a body fat percentage with the equations below. Height, neck, waist, and hip are all entered in the same unit: inches for the first pair, centimeters for the second. For men, “waist” means the abdomen measurement taken at the navel.
Men, inches
BF% = 86.010 × log₁₀(waist − neck) − 70.041 × log₁₀(height) + 36.76
Women, inches
BF% = 163.205 × log₁₀(waist + hip − neck) − 97.684 × log₁₀(height) − 78.387
Men, centimeters
BF% = 495 / (1.0324 − 0.19077 × log₁₀(waist − neck) + 0.15456 × log₁₀(height)) − 450
Women, centimeters
BF% = 495 / (1.29579 − 0.35004 × log₁₀(waist + hip − neck) + 0.22100 × log₁₀(height)) − 450
In plain terms, a larger waist relative to your neck and height means a higher estimated body fat, and the logarithm captures that this relationship is not a straight line. The inch and centimeter versions use different constants and are not interchangeable: feeding centimeters into the inch formula, or the reverse, produces results several percentage points off. Because the two versions are not exact conversions of each other, the same person can see results a few tenths of a point apart depending on the unit used. This calculator always applies the formula that matches the unit you select.
US Navy body fat standards
The Navy sets a maximum allowable body fat percentage by sex and age group. These are the figures this calculator uses:
| Age | Men (max) | Women (max) |
|---|---|---|
| 18–21 | 22% | 33% |
| 22–29 | 23% | 34% |
| 30–39 | 24% | 35% |
| 40+ | 26% | 36% |
If you enter your age in the calculator, it tells you whether your result is within or above the maximum for your group. That is an informational comparison only. Standards get revised, and an official assessment follows the Navy's own procedure and current Physical Readiness Program documents, so verify against those if a number affects your service.
Body fat percentage categories
If you are not in the military, the Navy's maximums are not the most useful yardstick. These commonly published ranges, similar to those from the American Council on Exercise, put your number in plain-language context:
| Category | Men | Women |
|---|---|---|
| Essential fat | 2–5% | 10–13% |
| Athletes | 6–13% | 14–20% |
| Fitness | 14–17% | 21–24% |
| Average | 18–24% | 25–31% |
| Obese | 25%+ | 32%+ |
Essential fat is the minimum your body needs to function. It is not a target for most people, and staying at that level can be unhealthy. Ranges vary by source, age, and goals, and “average” is not the same as “ideal.” Body fat is one health indicator among many, so talk to a clinician about your own situation.
How accurate is the Navy method?
The Navy method is a screening estimate, not a laboratory measurement. The commonly reported margin of error is around 3–4 percentage points, so a result of 18% could plausibly reflect a true value anywhere from roughly 14% to 22%. Methods such as DEXA scans and underwater weighing are more precise but need equipment and an appointment, while the Navy method needs only a tape measure.
It is less reliable in a few situations:
- Very muscular people. A thick neck or waist can be muscle rather than fat, which skews the estimate.
- Very lean or very high body fat. The equations were derived from samples of Navy personnel and fit less well at the extremes.
- Measurement error. Tape placement, tension, posture, and breathing all matter, and a quarter inch can change the result noticeably.
- Different body shapes. People who carry fat mainly in the hips, arms, or legs rather than the abdomen may be estimated less accurately.
Its best use is as a low-cost way to track change over time, measuring the same way each time. A trend over several weeks is more informative than any single number. It is not a diagnosis, and anyone with health concerns should consult a qualified professional.
Frequently asked questions
What is the Navy body fat formula?
It is a pair of equations, one for men and one for women, that estimate body fat percentage from height and tape-measure circumferences. Men use height, neck, and abdomen measurements; women also add hips. Both apply a base-10 logarithm to a combination of those measurements, and each comes in an inch version and a centimeter version. The equations were published by Hodgdon and Beckett at the Naval Health Research Center in 1984.
How accurate is the Navy body fat calculator?
The commonly reported margin of error is roughly 3–4 percentage points compared with laboratory methods such as DEXA or underwater weighing. It tends to be less reliable for very muscular, very lean, or very high-body-fat people. Treat the result as an estimate, and use exactly the same measuring technique each time if you are tracking change.
What is the maximum body fat percentage allowed in the Navy?
Under the standards shown on this page, the maximum is 22% for men and 33% for women at ages 18–21, rising to 26% for men and 36% for women at age 40 and over. The full age table is above. Standards can be revised, so confirm against current official Navy guidance if the result matters for your service.
How do I measure my waist and neck correctly?
Use a flexible, non-stretch tape on bare skin. Measure the neck just below the larynx, the abdomen (men) level with the navel or the waist (women) at its narrowest point, and the hips (women) at their widest point. Keep the tape level and snug without pressing into the skin, measure at the end of a normal exhale, and take each measurement three times and average them.
Is the Navy method different for men and women?
Yes. Body fat is distributed differently on average in men and women, so the women's equation adds a hip measurement and uses its own constants. The measurement sites also differ slightly: men measure the abdomen at the navel, while women measure the waist at its narrowest point.
Does the Navy method work for muscular or very lean people?
It can be less reliable. The method infers body fat from your waist size relative to your neck and height, so a very thick neck built from muscle, or a waist that is large for reasons other than fat, can skew the estimate. If precision matters, a DEXA scan or an assessment by a qualified professional is a better option.
Should I use inches or centimeters?
Either. Choose whichever unit you measured in. The calculator uses the inch formula for inches and the centimeter formula for centimeters. The two versions have different constants, so the same measurements can give results a few tenths of a percentage point apart.
References
The circumference method originates from the studies below and is the method used in the Navy's Physical Readiness Program for body composition assessment.
- Hodgdon JA, Beckett MB. “Prediction of Percent Body Fat for U.S. Navy Men from Body Circumferences and Height.” Naval Health Research Center, San Diego, CA; 1984.
- Hodgdon JA, Beckett MB. “Prediction of Percent Body Fat for U.S. Navy Women from Body Circumferences and Height.” Naval Health Research Center, San Diego, CA; 1984.
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Reviewed by the TecDit team · Last updated September 22, 2026
This calculator is provided for informational and educational purposes only and is not a substitute for professional fitness or medical assessment.
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