Quick Calculators

Body Fat Calculator

Estimate your body fat percentage and lean body mass using the highly accurate U.S. Navy Method.

EssentialFitnessAcceptableObese

Body Fat Percentage

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0 lbs
Fat Mass
0 lbs
Lean Mass

The U.S. Navy Method

This calculator uses the U.S. Navy circumference method to estimate body fat. It is widely considered one of the most accurate ways to measure body fat at home without expensive medical equipment like DEXA scans or water displacement tanks.

Tips for measuring: Use a flexible tape measure. Measure your neck just below the larynx (Adam's apple). Measure your waist at the navel (men) or at the narrowest point (women). For women, measure hips at the widest point.

Last updated: July 2026

The Formula

This calculator uses the U.S. Navy circumference formula developed by the Naval Health Research Center. For men:

Body Fat % = 495 / (1.0324 − 0.19077 × log₁₀(waist − neck) + 0.15456 × log₁₀(height)) − 450

For women, hip circumference is added to the equation:

Body Fat % = 495 / (1.29579 − 0.35004 × log₁₀(waist + hip − neck) + 0.22100 × log₁₀(height)) − 450

All measurements in this formula are in centimeters — the calculator converts inches automatically if you use Imperial units, so your result is accurate regardless of which unit you enter.

Worked Example

Using the calculator's default male inputs — 160 lbs, 70 inches (5'10") tall, 15-inch neck, 32-inch waist:

  • Converted to cm: height 177.8, neck 38.1, waist 81.28
  • Body Fat ≈ 13.4%
  • Fat Mass ≈ 21.5 lbs (9.7 kg)
  • Lean Mass ≈ 138.5 lbs (62.8 kg)

This calculator provides an estimate based on a validated but imprecise circumference method (typically accurate to within 3-4% of clinical methods). It is not a substitute for medical body composition testing. Talk to a doctor or registered dietitian about your individual health goals.

Frequently Asked Questions

It's generally accurate to within about 3-4% of more precise methods like DEXA scans or hydrostatic weighing, making it a solid at-home estimate rather than a clinical-grade measurement.
Height, neck, and waist for men. Height, neck, waist, and hips for women. All measured with a flexible tape measure, in either inches or centimeters.
Men measure at the navel. Women measure at the narrowest point of the torso, not necessarily at the navel.
The Navy method uses neck circumference as a reference point that correlates with lean body mass, which helps the formula separate fat tissue from muscle and bone when estimating body fat from waist size alone.
The underlying Navy formula was developed using centimeter measurements. This calculator automatically converts inches to centimeters behind the scenes if you use Imperial units, so your result is accurate either way.
General ACE guidelines put essential fat at 2-5% (men) or 10-13% (women), with 14-24% (men) or 21-31% (women) generally considered fit to acceptable. These are population guidelines, not personal medical targets.
You can, but treat trends over several weeks as more meaningful than any single reading. Small differences in tape placement, hydration, and posture between measurements can shift the result by a percentage point or more.