Body Fat Calculator

Estimated Body Fat
18.2%
Fitness

📊 Body Fat Categories (US Navy Method)

What Is a Body Fat Calculator?

This body fat calculator estimates your body fat percentage using the US Navy circumference method — a tape-measure-based formula developed for military fitness assessments that's widely used because it requires no special equipment.

How to Use the Body Fat Calculator

  1. Select your sex.
  2. Measure and enter your height.
  3. Measure your neck circumference (just below the larynx) and waist circumference (at the navel).
  4. Women also enter hip circumference (at the widest point).
  5. Your estimated body fat percentage and category appear instantly.

US Navy Body Fat Formula

Men
BF% = 86.010 × log10(waist − neck) − 70.041 × log10(height) + 36.76
Women
BF% = 163.205 × log10(waist + hip − neck) − 97.684 × log10(height) − 78.387

All measurements are in inches for this formula. Measure with a flexible tape at the specific landmarks described above for best accuracy.

Worked Example

Example: Male, Height 68", Neck 15", Waist 34"

BF% = 86.010 × log10(34 − 15) − 70.041 × log10(68) + 36.76

BF% = 86.010 × log10(19) − 70.041 × log10(68) + 36.76

Result: approximately 18.4% body fat — within the "acceptable" category for men.

Understanding Your Results

Body fat percentage tells you what proportion of your total weight is fat versus lean mass (muscle, bone, organs, water). Unlike BMI, it directly reflects body composition rather than weight relative to height, which is why two people with the same BMI can have very different body fat percentages.

Accuracy Notes

  • The Navy method is reasonably accurate for most people but less precise than DEXA scans, hydrostatic weighing, or calipers.
  • Measurement technique matters a lot — inconsistent tape placement or tension can shift results by several percentage points.
  • Track the trend over time rather than treating any single reading as exact.

Common Mistakes to Avoid

  • Measuring waist above or below the navel instead of at it, which skews the reading.
  • Pulling the tape too tight or too loose — it should sit snug but not compress the skin.
  • Comparing results across different measurement methods (e.g., calipers vs. Navy method) as if they're interchangeable.

Frequently Asked Questions

It's generally within a few percentage points of more precise clinical methods like DEXA scans for most body types, making it a reasonably good at-home estimate.

For men, roughly 14–24% is often considered the "fitness" to "acceptable" range; for women, roughly 21–31%, though healthy ranges vary by age and individual factors.

At the navel, standing relaxed, without pulling in your stomach — keep the tape level and snug but not compressing the skin.

Men and women naturally carry and distribute body fat differently, so the US Navy method uses separate formulas — the women's version also includes a hip measurement.

Body fat percentage more directly reflects body composition, while BMI is a simpler weight-to-height ratio that doesn't distinguish fat from muscle. Both are useful screening tools with limitations.

DEXA scans, hydrostatic (underwater) weighing, and Bod Pod air displacement are considered more precise than tape-measure methods, though they require specialized equipment not available at home.