How accurate is the US Navy method?

The US Navy circumference method has an error of ±3–4% compared to DEXA (dual-energy X-ray absorptiometry) scans, which are considered the gold standard. It is more accurate than BMI for estimating body composition but less precise than hydrostatic weighing or DEXA.

Where exactly should I measure?

Waist: at the navel level, horizontal. Neck: just below the larynx (Adam's apple), sloping slightly downward to the front. Hip (women only): at the widest horizontal circumference. All measurements should be taken without clothing and while relaxed (not flexed).

What is a healthy body fat percentage?

According to the American Council on Exercise (ACE): men - athletes 6–13%, fitness 14–17%, average 18–24%, obese 25%+. Women - athletes 14–20%, fitness 21–24%, average 25–31%, obese 32%+. Essential fat (minimum for survival) is approximately 2–5% for men and 10–13% for women.

Body Fat Percentage Calculator

How the US Navy method works

The US Navy body fat formula estimates body fat percentage from circumference measurements - no scale required. The formula uses logarithms to relate the ratio of waist-to-neck (and for women, waist+hip-to-neck) circumferences to body fat:

Men: BF% = 495 ÷ (1.0324 − 0.19077 × log₁₀(waist−neck) + 0.15456 × log₁₀(height)) − 450
Women: BF% = 495 ÷ (1.29579 − 0.35004 × log₁₀(waist+hip−neck) + 0.22100 × log₁₀(height)) − 450

Body fat classifications (ACE)

The American Council on Exercise defines the following ranges:

Category	Men	Women
Essential fat	2–5%	10–13%
Athletes	6–13%	14–20%
Fitness	14–17%	21–24%
Average	18–24%	25–31%
Obese	25%+	32%+

This calculator is for general information and is not medical advice. Consult a healthcare professional for personalized guidance.

How to take accurate measurements

Measurement technique significantly affects accuracy. Follow these guidelines:

Waist: measure at the narrowest point of the torso, usually about 1 inch above the navel. Keep the tape horizontal. Measure at the end of a normal exhale - not sucked in.
Neck: measure just below the larynx (Adam's apple), keeping the tape horizontal and perpendicular to the long axis of the neck.
Hips (women only): measure at the widest point of the hips and buttocks, keeping the tape horizontal.
Take each measurement twice and average the results if they differ by more than 0.5 cm.

Method comparison

Method	Equipment needed	Typical accuracy	Notes
US Navy (circumference)	Tape measure	±3–5%	Free, no scale needed; less accurate for very muscular or obese individuals
BMI-derived estimate	Scale, height measure	±5–8%	Very rough; does not distinguish fat from muscle
Skinfold calipers	Calipers (low cost)	±3–5%	Technique-dependent; most accurate in trained hands
Bioelectrical impedance (BIA)	BIA scale or handheld	±3–8%	Affected by hydration; convenient for tracking trends
DEXA scan	Clinical scanner	±1–2%	Gold standard; also measures bone density; costs $50–$150 at clinics