How is body fat percentage calculated?

This calculator uses the US Navy circumference method, which estimates body fat from measurements of the neck, waist, and hips (for women) along with height. It is considered accurate within 3–4% for most people.

What is the most accurate way to measure body fat?

DEXA scans are the gold standard but require medical equipment. The Navy method used here is accurate within 3–4% for most people and requires only a tape measure. Hydrostatic weighing and Bod Pod are also highly accurate alternatives.

Free Tool

Body Fat Percentage Calculator

Estimate your body fat percentage using the US Navy circumference method — the same formula used by the US military. Just a tape measure, no equipment needed.

By ChromaFit Team · Last updated Feb 17, 2026

Biological Sex

Units

Height

ft in

Weight (lbs)

Neck (inches) Measure at the narrowest point

Waist (inches) Men: at navel · Women: narrowest point

Hips (inches) Women only — widest point

Body Fat Percentage

—

Fat Mass

—

lbs

Lean Mass

—

lbs

Track Your Body Composition Over Time

ChromaFit's Physique Lab uses AI to score your muscle groups from a photo — so you can see exactly which areas are improving as your body fat drops.

Body Fat Percentage Ranges

Use these ranges to interpret your result:

Category	Men	Women
Essential Fat	2–5%	10–13%
Athletes	6–13%	14–20%
Fitness	14–17%	21–24%
Acceptable	18–24%	25–31%
Overweight	25%+	32%+

How the Navy Method Works

The US Navy circumference method estimates body fat using height and circumference measurements at specific body sites. It requires no special equipment — just a flexible tape measure. The formulas are:

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

The Navy method is accurate within 3–4% for most people and is widely used in military, clinical, and fitness settings as a practical alternative to DEXA scans.

Frequently Asked Questions

How accurate is the Navy method?

Within 3–4% for most people when measurements are taken correctly. It's less precise than DEXA but far more practical — no equipment, no cost, no appointment needed.

What is a healthy body fat percentage?

For men, 6–17% is athletic to fitness range. For women, 14–24%. These ranges are associated with good cardiovascular health and visible muscle definition.

How often should I measure?

Every 4–6 weeks. Body fat changes slowly — measuring too frequently shows noise, not progress. Track the trend over months, not days.

How do I measure correctly?

Use a flexible tape measure. Keep it level and snug but not tight. Measure at the same time of day (morning is most consistent) and in the same location each time.