Health Tool

Body Fat Calculator

Estimate your body fat percentage using the US Navy method. Enter your body measurements to see your body fat %, fat mass, lean mass, and fitness category.

Uses the US Navy circumference-based method - no calipers or equipment needed

Calculate Body Fat Percentage

Gender

The formula differs by gender

Units

Choose your preferred measurement system

Height (in)

e.g. 70 for 5'10"

Weight (lbs)

e.g. 180

Neck Circumference (in)

Measured just below the Adam's apple

Waist Circumference (in)

Measured at the navel level

How to Use This Body Fat Calculator

Take Your Measurements

Using a flexible tape measure, measure your neck, waist, and hips (women only) circumference. Keep the tape snug but not compressing the skin.

Enter Your Details

Select your gender and measurement units, then enter your height, weight, and circumference measurements in the calculator above.

Review Your Results

View your estimated body fat percentage, fat mass, lean mass, and fitness category. Use the reference table below to understand your results.

The US Navy Body Fat Formula

Men

%BF = 495 / (1.0324 - 0.19077 x log10(waist - neck) + 0.15456 x log10(height)) - 450

Women

%BF = 495 / (1.29579 - 0.35004 x log10(waist + hip - neck) + 0.22100 x log10(height)) - 450

The US Navy method (also known as the circumference-based method) was developed by Hodgdon and Beckett at the Naval Health Research Center. It uses simple body measurements to estimate body fat percentage.

Key details about this method:

All measurements must be in centimeters for the formula (the calculator converts inches automatically)
Women need an additional measurement (hip circumference) because fat distribution differs between genders
Fat mass = Body Weight x (Body Fat % / 100)
Lean mass = Body Weight - Fat Mass

This method is considered accurate within 1-3% of more expensive methods like DEXA scanning or hydrostatic weighing for most healthy adults.

Body Fat Category Reference

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%+

Ranges are based on guidelines from the American Council on Exercise (ACE)

Frequently Asked Questions

How accurate is the US Navy body fat method?

The US Navy method is generally accurate within 1-3% of more precise methods like DEXA scans for most people. It tends to be less accurate for very lean individuals (under 10% body fat) or those with unusual body proportions. For a free, at-home measurement, it provides a reliable estimate that is good enough for tracking progress over time.

Where exactly should I measure my waist, neck, and hips?

Neck: measure just below the larynx (Adam's apple), with the tape sloping slightly downward at the front. Waist: measure at the navel (belly button) level for men, and at the narrowest point of the waist for women. Hips (women only): measure at the widest point of the buttocks. Keep the tape snug but not compressing the skin, and stand relaxed without sucking in your stomach.

What is a healthy body fat percentage?

Healthy body fat ranges vary by gender. For men, 14-17% is considered "fitness" level, while 18-24% is "average" and healthy. For women, 21-24% is "fitness" level, and 25-31% is "average" and healthy. Athletes typically have lower body fat (6-13% for men, 14-20% for women). Going below essential fat levels (2-5% men, 10-13% women) is dangerous and not recommended.

Why is body fat percentage different for men and women?

Women naturally carry more body fat than men due to biological differences related to hormones and reproductive function. Estrogen promotes fat storage in the hips, thighs, and breasts. Essential fat for women (10-13%) is significantly higher than for men (2-5%) because this fat is necessary for normal hormonal function and fertility.

How often should I measure my body fat percentage?

For tracking progress, measure every 2-4 weeks under consistent conditions: same time of day, same hydration level, and using the same measurement technique. Daily measurements will show too much variation due to water retention, food intake, and measurement error. Consistent timing (such as first thing in the morning) gives the most reliable trend data.

Authoritative sources

Peterson DD — History of the U.S. Navy Body Composition program (Mil Med, 2015)
Confirms the provenance of the method above: the Navy assesses body composition with body-fat prediction equations based on circumference measurements, developed through Naval Health Research Center studies.
Shake CL, Schlichting C, et al. — Predicting percent body fat from circumference measurements (Mil Med, 1993)
Independent validation of the Naval Health Research Center circumference equation against hydrostatic weighing; reports a 6.8 to 18 percent false-positive rate and advises caution using it for individual decisions.
Babcock CJ, Kirby TE, et al. — A comparison of military circumference equations to skinfold-based equations (Mil Med, 2006)
The evidence behind the accuracy caveat on the result card: circumference equations correlate only moderately (r = 0.76-0.79) with skinfold estimates and read higher on average.
Gallagher D, Heymsfield SB, et al. — Healthy percentage body fat ranges: an approach for developing guidelines based on body mass index (Am J Clin Nutr, 2000)
Peer-reviewed derivation of healthy body-fat percentage ranges by sex, age and ethnicity, tied to the NIH and WHO BMI limits — the published basis for reading a percentage as healthy or not.
CDC — About Body Mass Index (BMI)
Backs the note that this is a screening estimate rather than a clinical measurement: dual-energy X-ray absorptiometry (DEXA) is the method that precisely measures body composition.

Important Disclaimer

This calculator provides body fat estimates for informational purposes only using the US Navy circumference method. It is not a substitute for professional medical advice, clinical body composition analysis, or DEXA scanning. Results may be less accurate for individuals with unusual body proportions, very low body fat, or high muscle mass. Consult a healthcare professional for personalized guidance on body composition and fitness goals.

Published by Kalcify · Last updated August 2, 2026

Calculators are built against primary sources — government tax authorities (IRS, HMRC, CRA, ATO) for finance and the World Health Organization for health metrics. Updated when rates or rules change. View methodology and data sources.

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