Body Fat Calculator: Navy Method and BMI
Estimate your body fat percentage with the U.S. Navy tape method or a BMI-based formula, then see where you land on the ACE body fat categories.
TL;DR
A body fat calculator estimates your body fat percentage from simple measurements. The U.S. Navy method uses your neck and waist (plus hips for women): for men, %BF = 86.010 x log10(waist minus neck) minus 70.041 x log10(height) plus 36.76. This calculator also offers a quicker BMI-based estimate.
Body fat
16.5%
Category: Fitness
Fat mass
30.6 lb
Lean mass
154.4 lb
BMI
26.5
See Your Full Body Composition
PR Streak tracks your body weight, body fat and 11 body measurements with charts, so you can watch your body fat percentage trend as you train.
How This Body Fat Calculator Works
Choose the Navy method for a tape-measurement estimate, or BMI for a quicker calculation from just your height, weight and age. Enter your numbers and this body fat calculator returns your body fat percentage, fat mass, lean mass and category.
The Navy method suits most lifters better since it measures your body directly. BMI can't tell muscle from fat, so it fits typical body types better than muscular or very lean lifters.
The U.S. Navy Body Fat Method
This is the classic Navy/DoD tape-measurement formula, developed by Hodgdon and Beckett in 1984 and used by the U.S. military for decades. Measure your neck, and for men your abdomen at the navel; women also measure the waist at its narrowest point and the hips at their widest.
Men: %BF = 86.010 x log10(abdomen - neck) - 70.041 x log10(height) + 36.76. Women: %BF = 163.205 x log10(waist + hip - neck) - 97.684 x log10(height) - 78.387. All measurements are in inches.
Example: a man 70 inches tall with a 15-inch neck and a 34-inch abdomen comes out to 17.5% body fat.
Since a Department of Defense memo in late 2025, the U.S. military's primary body composition screen is waist-to-height ratio under 0.55, not this tape formula. See the Army body fat calculator for that current standard.
The BMI Body Fat Method
The BMI method estimates body fat from your BMI, age and sex, with no tape measurements: %BF = 1.20 x BMI + 0.23 x age - 10.8 x sex - 5.4 (sex = 1 for men, 0 for women).
It comes from a study of 1,229 people, with a standard error of about 4.1% body fat, and it slightly overestimated body fat in obese subjects. Because BMI can't tell muscle from fat, tape measurements suit muscular lifters better.
Body Fat Percentage Categories
The American Council on Exercise (ACE) groups body fat percentage into categories, from essential fat up to obese, with separate ranges for men and women.
ACE body fat categories, by sex
| Category | Women | Men |
|---|---|---|
| Essential fat | 10-13% | 2-5% |
| Athletes | 14-20% | 6-13% |
| Fitness | 21-24% | 14-17% |
| Average | 25-31% | 18-24% |
| Obese | 32%+ | 25%+ |
Body Fat and the Military Standard
The U.S. military no longer relies on tape-measurement body fat formulas like the Navy method above as its main test. Since a Department of Defense memo in December 2025, waist-to-height ratio under 0.55 is the primary body composition screen. The Army body fat calculator covers that current standard and the tape test it replaced.
How Accurate Is the Navy Body Fat Calculator?
The Navy tape method is a well-studied field estimate, not a lab measurement like DEXA or hydrostatic weighing. Measuring carefully, at the exact points described above, matters more for accuracy than which formula you use.
The BMI method carries a standard error of about 4.1% body fat and tends to overestimate body fat in obese subjects. BMI also can't tell muscle from fat, which is why tape measurements suit muscular lifters better.
Used by lifters following PPL, 5x5, upper/lower, and more.
Frequently Asked Questions
What's my body fat percentage?
Enter your height, weight and either your neck and waist (Navy method) or your age (BMI method) into the calculator above to get a body fat percentage estimate, along with your category, fat mass and lean mass.
How accurate is the Navy body fat calculator?
It's a well-studied field method, not a lab measurement like DEXA, and its accuracy depends mostly on measuring your neck, waist and hips carefully at the exact points the method describes. Used correctly, it's accurate enough to track your trend over time.
What is the Navy method for body fat?
It's the U.S. Navy/DoD tape-measurement formula using your neck, height and, for men, abdomen at the navel, or for women, waist and hips. It's calculated from those measurements with a logarithmic formula, no scale or calipers needed.
Is BMI or the Navy method more accurate for body fat?
The Navy tape method is generally closer for muscular or very lean lifters, since BMI can't distinguish muscle from fat. The BMI-based formula carries a standard error around 4.1% body fat and slightly overestimates body fat in obese subjects.
Does this body fat calculator work for men and women?
Yes. Both the Navy tape method and the BMI method use separate formulas for men and women, and your result is shown against ACE's body fat category ranges for your specific sex.
What is a healthy body fat percentage?
It depends on your goals. ACE puts the "fitness" range at 14-17% for men and 21-24% for women, with the "average" range running higher. See the category chart above for the full breakdown.
How does the military measure body fat now?
Since a Department of Defense memo in late 2025, the primary standard is waist-to-height ratio under 0.55, not a tape-measurement formula. See the Army body fat calculator for that standard.
Sources
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