The Navy Body Fat Method Explained
The Navy method estimates body fat from a tape measure and your height. It's quick, free and surprisingly useful, as long as you know its limits.
The Navy body fat method estimates your body fat percentage from your height and a few tape measurements: neck and waist for men, plus hips for women. It was developed by the US Navy as a quick field test, and it's still one of the most practical ways to estimate body fat at home. It's not precise for any single reading, but measured consistently it's a good way to track whether you're trending in the right direction.
Here's how it works, how to measure properly, a worked example and how to interpret the result.
How the Navy method works
The idea is simple. Body fat tends to collect around the waist, and the neck gives a rough proxy for frame size and muscle. A bigger waist relative to your neck and height suggests more fat. For women, hip circumference is added because women typically store more fat around the hips and thighs.
The formulas, using centimetres, are:
| Formula | |
|---|---|
| Men | 495 / (1.0324 - 0.19077 x log10(waist - neck) + 0.15456 x log10(height)) - 450 |
| Women | 495 / (1.29579 - 0.35004 x log10(waist + hip - neck) + 0.22100 x log10(height)) - 450 |
You don't need to do the maths by hand. Our body fat calculator uses the Navy formula and does it for you. The important part is getting the measurements right.
How to take the measurements
Measurement technique matters more than anything else with this method. A centimetre off on your waist can shift your result by a full percentage point or more.
- Use a flexible, non-stretch tape measure. A cloth sewing tape or a dedicated body tape works well.
- Measure in the morning, before eating or drinking much, after using the bathroom.
- Height: stand barefoot against a wall, heels together, looking straight ahead.
- Neck: measure just below the larynx (Adam's apple), with the tape sloping slightly down toward the front. Don't flare your neck or tense it.
- Waist (men): measure horizontally at the level of the navel. Relax your stomach and measure at the end of a normal exhale. Don't suck in.
- Waist (women): measure at the narrowest point of the natural waist, usually above the navel, also at the end of a normal exhale.
- Hips (women only): measure around the widest part of the buttocks, feet together.
- Take each measurement two or three times and use the average.
The tape should sit snugly on the skin without compressing it. Use a mirror to make sure it's level all the way around, or ask someone to help.
A worked example
Let's say a man is 180 cm tall, with a 38 cm neck and an 85 cm waist.
- Waist minus neck: 85 - 38 = 47 cm
- Plug that and his height into the men's formula.
- Result: roughly 16% body fat.
Now imagine he loses some fat over a couple of months and his waist drops to 81 cm, with his neck unchanged. The formula now gives around 13%. That four-centimetre waist change is the kind of shift that often starts to reveal the upper abs.
For a woman who is 165 cm tall, with a 32 cm neck, a 72 cm waist and 98 cm hips, the women's formula gives roughly 27%.
To see where those numbers sit, our body fat percentage chart describes what different levels typically look like.
How accurate is it?
The honest answer: reasonably good on average, less reliable for individuals.
Studies comparing tape-based formulas with lab methods generally find that they're in the right ballpark for groups of people, but an individual result can be several percentage points off. A few things push it off:
- Muscular people with thick necks can get underestimated body fat, because a bigger neck lowers the result.
- People who carry fat mostly on the hips and legs (common in women) or mostly on the back may be misjudged.
- Inconsistent measuring is the biggest source of error by far.
- Bloating or a big meal can add a centimetre or two to the waist.
So treat a single number as a rough estimate, not a fact. The real value of the Navy method is tracking change over time with consistent technique.
How it compares with other methods
| Method | Cost | Convenience | Typical use |
|---|---|---|---|
| Navy tape method | Very low | High | Trend tracking at home |
| Skinfold calipers | Low | Medium, needs practice | Trend tracking, more skill-dependent |
| Smart scales (BIA) | Low to medium | Very high | Easy, but affected by hydration |
| DEXA scan | High | Low | Detailed body composition snapshot |
| Visual estimate or photos | Free | High | Rough guide, best combined with others |
No home method is perfect. For a fuller comparison, read our guide on how to measure body fat at home.
How to use the Navy method well
- Measure every one to two weeks, not every day. Daily changes are mostly water and food.
- Use the same tape, time and position each time.
- Track your waist on its own too. Waist circumference is one of the most useful single numbers for fat loss progress. The waist-to-height ratio calculator turns it into a simple health-oriented metric.
- Pair it with photos and scale weight. If all three trend in the same direction, you can be confident.
- Don't chase a precise number. Focus on the direction of change.
What Navy body fat means for abs
If your goal is visible abs, the Navy result can tell you roughly how far you have to go. Many men begin to see some ab outline in the low-to-mid teens, and many women in the high teens to low twenties, though genetics and ab thickness change this a lot. Our article on what body fat percentage you need to see abs explains the range, and the how long to get abs calculator turns the gap into a rough timeline.
If your number is higher than you'd like, the fix is the same as always: a moderate calorie deficit, enough protein, resistance training and patience. Body fat percentage is just one measure of health. If you have concerns about your weight, eating or health, talk to a doctor.
Where AbShred fits
The Navy method gives you a number from a tape measure. AbShred, an iPhone app that's coming soon, takes a different approach: it estimates a body-fat range from one photo and scores six ab zones, with weekly rescans in the same light. Using a tape method alongside a photo-based estimate gives you two independent views of the same trend. Both are estimates, and AbShred is for fitness motivation, not medical measurement. Join the waitlist at abshred.com.
FAQ
Is the Navy body fat method accurate?
It's reasonably accurate on average but can be several percentage points off for an individual. It's best used for tracking trends with consistent measurements.
Where do you measure your waist for the Navy method?
Men measure horizontally at the navel. Women measure at the narrowest part of the waist. Measure relaxed, at the end of a normal breath out.
Why do women measure their hips?
Women typically store more fat around the hips and thighs, so including hip circumference makes the estimate more representative.
Does the Navy method work for muscular people?
It can underestimate body fat in people with very thick, muscular necks. It's still useful for trends, but the absolute number may be off.
How often should I measure with the Navy method?
Every one to two weeks under the same conditions is plenty. More frequent measurements mostly pick up water and food changes.