Body-Fat Percentage Calculator

Using the Navy Method

How the Calculator Works

The Navy Tape Measure Method was developed by Dr. Hodgdon and Dr. Beckett for the U.S. Navy. It's popular because of how easy it is. All you need is measuring tape and a bathroom scale. Some bathroom scales have a built-in bioelectrical impedance analysis (BIA), but the Navy Method is more accurate.

The other advantage of the Navy Method is that it does a reasonably good job of differentiating between muscle and fat. You don't need to be in good shape to use it, but as you build muscle and/or lose fat, it should do a good job of recognizing your progress. BIA bathroom scales are terrible for that.

  • Your waist measurement is a proxy for body fat. The thicker your waist, the higher your body fat percentage. A thicker waist is also associated with poorer health, especially if it climbs over 40 inches (100 cm). Gaining muscle in your abs, obliques, and lower back muscles will also increase your waist size, but that's good. This calculator is built for the Navy. These people tend to be muscular.
  • Your neck measurement is used as a proxy for muscle mass. If you have a thick neck and a thick waist, you're probably overweight. If you have a thin neck and a small waist, you're probably thin. If you have a thick neck and a small waist, you're probably muscular. This can backfire if you bulk up without training your neck, giving you a proportionally thin neck.
  • Hip measurements are only used for women. Women tend to store less fat in their stomachs and more in their thighs and hips. The calculator takes that into account.

The more unusual your build, the less accurate the calculator will be. Some people are born with thicker waists. Some naturally skinny guys (like me) have unusually thin necks until they train them.

This calculator should get you within 3–4% of your true body-fat percentage, but it won't always. Even fancier methods like DEXA can be off by as much as 8% in rare cases.

The Best Ways to Estimate Body Fat

There are a few different ways to estimate your body fat percentage:

  • The 4-Compartment (4C) model is what researchers use. It combines several different methods. It isn't available to regular people, and it's overkill anyway.
  • DEXA is the best way the average person can measure their body fat. However, it's expensive and inconvenient, and it doesn't work well on everyone.
  • BodPod and hydrostatic weighing are nearly as good as DEXA, but they're similarly expensive and even more inconvenient.
  • BIA scales vary in quality, but the 2-point ones you use at home are easily confused by changes in muscle mass. Building muscle shows up as fat gain. Losing muscle shows up as fat loss. Don't trust them.
  • Skinfold callipers are great for tracking body fat changes at home. They don't measure the visceral fat underneath your muscles, which is the type of fat that impacts your health, but they can still be great for measuring progress. The downside is that you need to buy callipers, learn how to use them, and then spend quite a lot of time fiddling with measurements and formulas.
  • The Navy Method is simple and easy. All you need is a measuring tape. It's the most accurate of the at-home methods. It also works well for people who exercise and lift weights.

If you're estimating your body-fat percentage to get an idea of how many calories you should eat while bulking, cutting, or recomping, the Navy Method is more than accurate enough.

If you're tracking your calories with the MacroFactor app, it uses a visual method of estimating your body-fat percentage. That's perfectly fine, too. Anything that gets you within 5% of your true body-fat percentage is close enough.

How to Track Body Fat Changes

The Navy Method is good at tracking changes in your body fat percentage, especially if you train your abs, lower back, and neck.

You don't need to use the Navy Method to track your progress, though. Instead, I recommend measuring your waist circumference, shoulder circumference, and all the body parts you care about. In our Bony to Beastly and Outlift Hypertrophy programs, we track:

  1. Waist circumference at the height of your belly button. If the measurement goes down, you’re probably losing fat. If it goes up a little bit, you might be building bigger core muscles, gaining fat, or both.
  2. Shoulder circumference at the widest point. The more muscle you build in your shoulders, chest, and upper back, the greater your shoulder circumference will grow. While bulking, your shoulder growth should outpace your waist growth by a generous margin. When cutting, your waist should shrink faster than your shoulders. When recomping, we want to see your shoulder-to- waist ratio grow gradually larger.
  3. Biceps, flexed. Measure your biceps at the widest point, flexed but “cold”—without a muscle pump. Gaining even an inch in your upper arms will have a massive impact on your strength and appearance. We want to see about inch for every 10–20 pounds you gain.
  4. Forearms. Measure your forearms with your arms held straight out ahead, with your hands clenched, just below the elbow at the widest point. You can train your forearms if you want to grow them faster.
  5. Hips at the widest point. This is to measure your glutes— perhaps the most important muscles for athletic performance, preventing back pain, and improving your assthetics.
  6. Thighs, halfway between your hips and knees. This is to measure the size of your quads and hamstrings. If you wimp out on leg day, these measurements will become more similar to those of a chicken.
  7. Calves. Most bodybuilders believe your calves should be about the same size as your upper arms. Athletic and running performance seems to have more to do with tendon stiffness than calf size, so I'm not sure it matters outside of bodybuilding.

If your asymmetries aren’t causing you problems, you only need to measure your more impressive side. Your bigger arm determines your official arm size. Your weaker arm decides how much weight you lift and how many reps you do. That should give you a pleasantly balanced physique.

If your asymmetries are causing you problems—pain, performance issues, or aesthetic woes—let us know in the online coaching community. Everyone is asymmetrical in their own ways, for their own reasons. Marco will help you out one-on-one.

The Bony to Beastly Program

If you want a full muscle-building program, including a 5-month workout routine, a bulking diet guide, a gain-easy recipe book, and online coaching, check out our Bony to Beastly Bulking Program. Or, if you want a customizable intermediate bulking program, check out our Outlift Program.

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