Body Fat Calculator (Navy Method)
Estimate your body fat percentage using the US Navy tape-measure method with only a few simple circumference measurements. No calipers or lab equipment required — results are suitable for health and fitness tracking.
About this calculator
The US Navy circumference method estimates body fat by measuring specific body sites and applying a logarithmic density formula. For men: Body Fat % = 495 / (1.0324 − 0.19077 × log₁₀(waist − neck) + 0.15456 × log₁₀(height)) − 450. For women: Body Fat % = 495 / (1.29579 − 0.35004 × log₁₀(waist + hip − neck) + 0.22100 × log₁₀(height)) − 450. Waist, neck, hip, and height are all measured in centimeters. The formula was derived from underwater weighing data and uses circumference ratios as proxies for fat distribution. It is accurate to within approximately 3–4 percentage points for most healthy adults, making it more than sufficient for tracking progress over time, though DEXA scanning remains the gold standard for precision.
How to use
Example: a male with waist = 90 cm, neck = 38 cm, and height = 180 cm. Step 1: waist − neck = 90 − 38 = 52; log₁₀(52) ≈ 1.716. Step 2: log₁₀(180) ≈ 2.255. Step 3: Denominator = 1.0324 − (0.19077 × 1.716) + (0.15456 × 2.255) = 1.0324 − 0.3274 + 0.3485 = 1.0535. Step 4: Body Fat % = 495 / 1.0535 − 450 = 469.9 − 450 ≈ 19.9%. This falls in the fitness category for men (14–24%).
Frequently asked questions
How accurate is the Navy method for measuring body fat percentage compared to DEXA or hydrostatic weighing?
The US Navy method has been validated against hydrostatic weighing and typically falls within 3–4 percentage points of true body fat for most adults. DEXA (dual-energy X-ray absorptiometry) and hydrostatic weighing are considered gold standards with errors under 1–2%, but they require expensive equipment and clinical access. The Navy method is significantly more accessible and repeatable at home, making it excellent for tracking trends over weeks and months. Where accuracy matters clinically, DEXA is preferred; for general fitness monitoring, the Navy method is entirely adequate.
Where exactly should I measure my waist and neck circumference for the Navy body fat formula?
Waist circumference for men should be measured at the navel level while relaxed — do not suck in your stomach. For women, waist is measured at the narrowest point of the abdomen, typically just above the belly button. Neck circumference is measured just below the larynx (Adam's apple) with the tape horizontal and snug but not compressing the skin. Hip circumference (women only) is taken at the widest point around the buttocks. Consistency of measurement location across sessions is critical — small errors in placement can shift body fat estimates by 1–3 percentage points.
What is a healthy body fat percentage range for men and women?
For men, essential fat is around 2–5%, athletic range is 6–13%, fitness range is 14–24%, and above 25% is considered above average or obese. For women, essential fat is higher at 10–13% due to hormonal and reproductive functions, athletic is 14–20%, fitness is 21–31%, and above 32% is considered above average. These classifications come from the American Council on Exercise. Optimal body fat for health and longevity is generally in the fitness range, while very low levels (below essential fat) carry serious health risks including hormonal disruption and immune suppression.