Body Fat Percentage Calculator
Estimates your body fat percentage from simple tape measurements using the U.S. Navy circumference method. Ideal for tracking fat loss progress without calipers or expensive lab equipment.
About this calculator
The U.S. Navy body fat method uses body circumference measurements and height to estimate fat percentage via a logarithmic formula validated against hydrostatic weighing. For males: Body Fat % = 495 / (1.0324 − 0.19077 × log₁₀(waist − neck) + 0.15456 × log₁₀(height)) − 450. For females: Body Fat % = 495 / (1.29579 − 0.35004 × log₁₀(waist + hip − neck) + 0.22100 × log₁₀(height)) − 450, where all measurements are in centimetres. The formula leverages the observation that fat mass tends to accumulate around the waist and hips, while neck circumference serves as a proxy for lean mass. Research shows the Navy method has a standard error of roughly ±3–4% body fat compared to DEXA scans, making it a reliable field tool. Measure at the narrowest point for waist and the largest point for hips and neck for best accuracy.
How to use
Example: a male with height 178 cm, waist 85 cm, and neck 38 cm. Step 1 — Compute waist − neck: 85 − 38 = 47 cm. Step 2 — log₁₀(47) ≈ 1.6721; log₁₀(178) ≈ 2.2504. Step 3 — Denominator: 1.0324 − (0.19077 × 1.6721) + (0.15456 × 2.2504) = 1.0324 − 0.3190 + 0.3479 = 1.0613. Step 4 — Body Fat % = 495 / 1.0613 − 450 = 466.42 − 450 ≈ 16.4%. This falls in the 'fitness' category for adult males, which ranges from roughly 14–17% body fat.
Frequently asked questions
How accurate is the Navy method body fat calculator compared to DEXA?
The U.S. Navy circumference method typically falls within ±3–4 percentage points of DEXA (dual-energy X-ray absorptiometry), which is considered the clinical gold standard. Its accuracy is greatest for individuals with average body proportions and can be less reliable for very lean athletes or individuals with unusual fat distribution patterns. The method also relies heavily on measurement technique — small errors in tape placement can shift results by several percentage points. For tracking trends over time rather than absolute values, the Navy method is highly practical and repeatable.
Where exactly should I measure waist and neck circumference for the body fat calculator?
For waist circumference, measure at the narrowest point of your torso, typically just above the navel and below the rib cage, with the tape parallel to the floor. For neck circumference, measure just below the larynx (Adam's apple) with the tape perpendicular to the long axis of the neck. For hip circumference (females), measure at the widest point of the buttocks with the tape horizontal. Take each measurement twice and average them, and always exhale normally before measuring the waist — do not suck in or push out.
What body fat percentage is considered healthy for men and women?
For men, essential fat is around 2–5%, athlete range is 6–13%, fitness range is 14–17%, acceptable is 18–24%, and above 25% is typically classified as obese. For women, essential fat is 10–13%, athlete range is 14–20%, fitness is 21–24%, acceptable is 25–31%, and above 32% is generally considered obese. These classifications come from the American Council on Exercise (ACE) and are widely used by fitness professionals. Optimal body fat varies with age — slightly higher percentages are considered healthy as people get older.