How accurate is the US Navy body fat formula?

The US Navy method is widely considered the most accurate circumference-based estimation. In clinical studies, it typically demonstrates a correlation of 0.90+ with DEXA scans and hydrostatic weighing, with an average margin of error of +/- 3%.

What are the healthy body fat ranges for 2026?

Healthy ranges vary by age and sex. For men, 14-17% is considered 'fitness,' while 18-24% is 'average.' For women, 21-24% is 'fitness,' and 25-31% is 'average.' Anything below 5% for men or 12% for women is generally considered essential fat only.

Why does the calculator ask for neck and waist measurements?

The US Navy algorithm uses the ratio between your neck (representing lean structure) and your waist/hips (representing primary fat storage locations) to mathematically estimate total body density.

Is this body fat calculator private?

Yes. Kodivio processes all biometric data locally in your browser. We never upload your waist, hip, or neck measurements to our servers, ensuring 100% HIPAA-level privacy standards through local execution.

Precision Biometrics Suite

Body Fat Calculator

Moving Beyond BMI: Calculate your actual body composition with the clinically-validated US Navy circumference algorithm.

Measurements

Weight (kg)

Height (cm)

Waist (cm)

Neck (cm)

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Navy Method Calibrated

Provide your circumference measurements for a precision body composition estimate.

The Science of the Navy Method

The US Navy Body Fat Formula was developed at the Naval Health Research Center (NHRC) as a cost-effective yet statistically rigorous way to assess personnel fitness. Unlike BMI, which only measures weight relative to height, the Navy method accounts for abdominal adiposity and structural thickness.

By measuring the neck and waist (and hips for women), the formula effectively isolates the primary locations where the body stores subcutaneous and visceral fat, providing a much clearer picture of your metabolic health.

Physiological Standards (2026)

Essential Fat

2-5% (Men) | 10-13% (Women)

Required for organ protection.

Athletes

6-13% (Men) | 14-20% (Women)

Optimal performance range.

Fitness

14-17% (Men) | 21-24% (Women)

Excellent overall health.

Average

18-24% (Men) | 25-31% (Women)

Standard healthy range.

Obese

25%+ (Men) | 32%+ (Women)

Increased metabolic risk.

The "Bare Skin" Protocol

For accuracy within the +/- 3% range, you must measure directly against the skin. Clothing—even thin athletic wear—can add 0.5 to 1.5 inches to your waist measurement, significantly skewing the final fat percentage calculation.

Men

Waist at Navel

Women

Hips at Widest

In-Depth Health FAQ

Why is Body Fat more important than BMI?

Two people can have the same BMI but vastly different health profiles. One may have high muscle mass (low risk), while the other has 'normal' weight but high visceral fat (high metabolic risk). Body fat percentage isolates this variable.

What is Lean Body Mass (LBM)?

LBM is everything in your body that isn't fat: muscle, bone, organs, and water. Tracking LBM is vital during a weight loss phase to ensure you are losing fat rather than burning off metabolic muscle tissue.

When is the best time to measure?

Consistency is key. Measure first thing in the morning, after using the bathroom and before eating or drinking. This minimizes the impact of 'bloating' on your waist circumference.

Does the calculator store my data?

No. Kodivio implements a privacy-first JavaScript engine. Your measurements are processed in your local RAM and are never cached or sent to a database. Your biometrics stay on your machine.