Body Fat Calculator — Navy Method & BMI Method

Height

Neck circumference

Waist circumference

Hip circumference (women only)

Estimated Body Fat

—

Fat Mass

—

Lean Mass

About the Body Fat Calculator

This calculator uses the US Navy circumference method, developed by Hodgdon and Beckett (1984). It estimates body fat percentage from simple tape measure readings — no expensive equipment needed. The method is widely used by military and fitness professionals.

Body fat categories (American Council on Exercise)

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

How to take measurements

Measure at the same time each day (morning is best). Use a flexible tape measure. For waist, measure at the narrowest point (women) or navel level (men). For neck, measure just below the larynx. For hips (women), measure at the widest point.

Body fat percentage ranges by category

Body fat percentage is a more meaningful health metric than weight alone because it distinguishes between fat mass and lean mass (muscle, bone, organs). Two people of identical height and weight can have dramatically different body compositions and health profiles.

Essential fat (men 2-5%, women 10-13%) — minimum fat for physiological function
Athletic range (men 6-13%, women 14-20%) — typical for competitive athletes
Fitness range (men 14-17%, women 21-24%) — above average fitness and body composition
Average (men 18-24%, women 25-31%) — typical for moderately active adults
Obese (men 25%+, women 32%+) — associated with increased metabolic health risks

Frequently Asked Questions

How is body fat percentage calculated?

The US Navy method uses neck, waist, and hip measurements along with height to estimate body fat. The formula differs for men and women. The BMI method uses body mass index as a proxy.

What is a healthy body fat percentage?

For men, 6–24% is generally healthy; 25% and above is considered excess fat. For women, 16–30% is healthy; above 31% is considered excess. Athletes typically have lower percentages.

Is the Navy method accurate?

The Navy method has a margin of error of about 3–4 percentage points. It is more accurate than BMI-based estimates but less precise than DEXA scans or hydrostatic weighing.

Where should I measure my waist?

Measure your waist at the narrowest point (for women) or at the navel level (for men). Stand relaxed, do not suck in your stomach, and measure after exhaling normally.

What is the most accurate way to measure body fat?

DEXA (dual-energy X-ray absorptiometry) scan is the gold standard, giving accuracy within 1-2%. Hydrostatic weighing (underwater) is also very accurate. Skinfold calipers with a trained tester are accurate within 3-4%. BIA (bioelectrical impedance, used in smart scales) is the least accurate method, varying by 5-8% based on hydration.

Does body fat percentage change with age?

Yes. After about age 30, lean mass (muscle) naturally decreases by 3-8% per decade without resistance training — a process called sarcopenia. Because fat mass stays the same or increases while lean mass falls, body fat percentage rises with age even at a stable weight. Resistance training significantly slows this process.