How to Calculate Body Fat Percentage (US Navy Method)

Your bathroom scale tells you what you weigh, but it says nothing about what that weight is made of. Two people at 180 pounds can look completely different if one carries 15% body fat and the other carries 30%. Knowing your body fat percentage gives you a much clearer picture of your health and fitness than the number on the scale ever could.

The good news: you do not need expensive lab equipment. The US Navy body fat methodrequires only a tape measure, and it is accurate enough for the Department of Defense to use it as an official fitness standard. Let’s walk through exactly how it works.

Why Body Fat Percentage Matters

BMIis a useful screening tool, but it treats all weight the same. A muscular athlete can be flagged as “overweight” by BMI even though their body composition is excellent. Body fat percentage separates lean mass (muscle, bone, organs) from stored fat, giving you a far more actionable health metric.

Carrying excess body fat—especially visceral fat around the organs—is linked to increased risk of type 2 diabetes, heart disease, and metabolic syndrome. Tracking body fat over time helps you gauge whether your training and nutrition plan is actually working, regardless of what the scale says.

The US Navy Method Formula

The US Navy method uses circumference measurements and height to estimate body fat. The formulas differ for men and women because fat distribution patterns differ between sexes.

For Men

%BF = 86.010 × log₁₀(abdomen − neck) − 70.041 × log₁₀(height) + 36.76

All measurements are in inches. “Abdomen” is your waist measured at navel level.

For Women

%BF = 163.205 × log₁₀(waist + hip − neck) − 97.684 × log₁₀(height) − 78.387

Women need one additional measurement—hip circumference—because the formula accounts for the way women typically store more fat around the hips and thighs.

How to Take Your Measurements

Accuracy depends entirely on consistent, correct measurements. Grab a flexible cloth or plastic tape measure (not a metal one) and follow these guidelines.

Neck

Measure just below the larynx(Adam’s apple). Keep the tape level—do not angle it. Pull it snug against the skin without compressing it. Round downto the nearest half inch. For example, if you read 15.75″, record 15.5″.

Waist (Men)

Stand relaxed and measure at navel level. Do not suck in your stomach—breathe normally and measure at the end of a regular exhale. Round upto the nearest half inch. A reading of 33.25″ becomes 33.5″.

Waist (Women)

Measure at the narrowest point of your torso, typically a couple of inches above the navel. Round up to the nearest half inch using the same approach.

Hips (Women Only)

Stand with feet together and measure at the widest point of your buttocks and hips. Keep the tape level all the way around. Round up to the nearest half inch.

Worked Example: A 5′10″ Male

Let’s plug in some numbers to see the formula in action. Imagine a man who is 5′10″ tall with a neck circumference of 15.5″ and a waist at the navel of 34″.

First, convert height to inches: 5 × 12 + 10 = 70 inches.

Now calculate the two log terms:

• Abdomen − neck = 34 − 15.5 = 18.5
• log₁₀(18.5) = 1.2672
• log₁₀(70) = 1.8451

Plug into the formula:

%BF = 86.010 × 1.2672 − 70.041 × 1.8451 + 36.76

%BF = 108.99 − 129.23 + 36.76 = 16.52%

So this man has an estimated body fat of roughly 16.5%, which falls in the “Fitness” category. Not bad at all. Skip the math and get your result instantly with our body fat calculator.

Body Fat Percentage Ranges

Once you have your number, you need context. The American Council on Exercise (ACE) provides widely referenced categories:

Essential fatis the minimum your body needs to function properly—think cell membranes, nerve insulation, and hormone production. Dropping below that range is dangerous. For most people focused on general health, the Fitness range is a realistic and sustainable goal.

Note that women naturally carry more body fat than men due to reproductive and hormonal differences. A woman at 22% body fat and a man at 14% are in equivalent fitness categories.

Tips for Accurate Results

The Navy method is only as good as the measurements you feed it. Follow these tips to minimize error:

• Measure at the same time of day. Morning before eating is ideal. Waist circumference can fluctuate by over an inch throughout the day due to food, water, and bloating.
• Do not measure right after exercise. A post-workout pump temporarily increases circumference in certain muscle groups and can skew results.
• Take three measurements and average them. Measure each site three times, then use the average. This smooths out small tape placement errors and gives you a more reliable number.
• Use the same tape measure each time. Cloth tapes can stretch over months of use. If yours looks worn, replace it.
• Have someone else measure you if possible. It is hard to keep the tape perfectly level on your own back. A helper makes measurements more consistent, especially for hips.

How the Navy Method Compares to Other Techniques

No method short of dissection is 100% accurate. Here is how the most common approaches stack up:

• DEXA scan– Considered the gold standard. Uses low-dose X-rays to distinguish bone, lean tissue, and fat. Accuracy is within 1–2%, but a single scan costs $50–$150 and requires a clinical visit.
• Skinfold calipers– A trained technician pinches skin at 3–7 sites and measures fold thickness. Accuracy is around 3–4% when done by an experienced tester, but inter-tester variability is high.
• Bioelectrical impedance (BIA)– Found in smart scales and handheld devices. A small electrical current measures resistance through your body. Convenient but easily thrown off by hydration levels—error margins of 3–5% are common.
• US Navy tape method– Free, requires no special equipment, and studies show it correlates within 3–4% of DEXA for most people. It can underestimate body fat in very lean individuals and overestimate in very muscular ones, but for the general population it is remarkably practical.

For tracking trendsover time—which is what most people actually need—the Navy method is hard to beat. As long as you measure consistently, the direction of change will be accurate even if the absolute number is off by a point or two.

Next Steps

Grab a tape measure, follow the guidelines above, and run your numbers through the body fat calculator. Write down today’s result, then remeasure every two to four weeks. Pair it with your BMI for a more complete snapshot of where you stand.

Remember, the goal is not to obsess over a single number. Body fat percentage is one data point among many—energy levels, strength gains, sleep quality, and how your clothes fit all matter too. Use the number as a compass, adjust your nutrition and training, and measure again. Progress over perfection wins every time.