How accurate is the US Navy method?

It is typically within 3–4 percentage points of DEXA for most adults but can be less accurate at the extremes (very lean or very obese). It is, however, very repeatable, so it is excellent for tracking change over time.

How should I measure correctly?

Measure first thing in the morning, unclothed, with a flexible tape. Neck just below the larynx, waist at the navel level, and hip (women) at the widest point of the buttocks. Keep the tape level and snug but not compressing.

Why does the female formula include hip but the male formula doesn't?

Women tend to store more subcutaneous fat in the hips and thighs, so adding hip circumference improves accuracy for them. The male formula relies on neck-to-waist difference instead.

What is lean body mass?

Lean body mass is everything that is not fat — bone, muscle, water, organs. It is computed here as total weight × (1 − BF%).

Does this tool store my data?

No. Measurements are processed in your browser and cleared when you close the tab.

Is the body fat calculator free?

Yes — completely free, no signup or limits.

Body Fat Calculator

Estimate body fat % and lean body mass using the US Navy circumference method.

Written by Golam Rabbani, Founder & Lead Engineer — Last updated 2026-05-01

This interactive tool requires JavaScript. Read the formula and worked example below; you can compute the result by hand.

How to use this body fat calculator

Select your gender and your preferred length unit (cm or in).
Enter your height.
Measure your neck just below the larynx, and waist at the navel (women also measure the hip at the widest point) — enter all three.
Toggle kg/lbs and enter your body weight so fat mass and lean mass can be reported.
Press Calculate to see body-fat %, ACSM category, fat mass, and lean body mass.

About this body fat calculator

The body fat calculator uses the U.S. Navy circumference method, which estimates body-fat percentage from height plus neck, waist, and (for women) hip measurements. It then combines that percentage with your weight to give fat mass and lean body mass, and places the result in the ACSM's standard category bands (Essential / Athletes / Fitness / Average / Obese) with sex-specific cut-offs.

The equations are from Hodgdon JA, Beckett MB. "Prediction of percent body fat for U.S. Navy men and women from body circumferences and height" (Naval Health Research Center Technical Report 84-11, 1984). They take measurements in inches; this tool converts your cm inputs internally. Male: BF% = 495 / (1.0324 − 0.19077 × log10(waist − neck) + 0.15456 × log10(height)) − 450. Female: BF% = 495 / (1.29579 − 0.35004 × log10(waist + hip − neck) + 0.22100 × log10(height)) − 450. This is an estimate for informational purposes and is not a substitute for a DEXA scan or advice from a qualified clinician — circumference methods are typically ±3–4% absolute compared to DEXA.

For example, a male 180 cm tall (≈70.9 in) with a 40 cm neck (≈15.7 in) and 85 cm waist (≈33.5 in) gives BF% ≈ 495 / (1.0324 − 0.19077 × log10(33.5 − 15.7) + 0.15456 × log10(70.9)) − 450 ≈ 17.7%, "Fitness" category. If they weigh 80 kg, fat mass ≈ 14.2 kg and lean mass ≈ 65.8 kg. The tool is useful for tracking body composition over time without lab equipment.

FAQ

How accurate is the US Navy method?: It is typically within 3–4 percentage points of DEXA for most adults but can be less accurate at the extremes (very lean or very obese). It is, however, very repeatable, so it is excellent for tracking change over time.
How should I measure correctly?: Measure first thing in the morning, unclothed, with a flexible tape. Neck just below the larynx, waist at the navel level, and hip (women) at the widest point of the buttocks. Keep the tape level and snug but not compressing.
Why does the female formula include hip but the male formula doesn't?: Women tend to store more subcutaneous fat in the hips and thighs, so adding hip circumference improves accuracy for them. The male formula relies on neck-to-waist difference instead.
What is lean body mass?: Lean body mass is everything that is not fat — bone, muscle, water, organs. It is computed here as total weight × (1 − BF%).
Does this tool store my data?: No. Measurements are processed in your browser and cleared when you close the tab.
Is the body fat calculator free?: Yes — completely free, no signup or limits.