Body Fat Calculator

The Navy method uses the natural logarithm of a few circumference measurements, since fat tends to scale with the body in a roughly logarithmic pattern rather than a straight line. All measurements are in centimetres for the metric version of the formula.

Men: Body Fat % = 495 ÷ (1.0324 − 0.19077 × log₁₀(waist − neck) + 0.15456 × log₁₀(height)) − 450. Women: Body Fat % = 495 ÷ (1.29579 − 0.35004 × log₁₀(waist + hip − neck) + 0.22100 × log₁₀(height)) − 450.

Measurement technique matters more than the formula itself. A tape pulled too tight or placed at the wrong landmark can shift your result by several percentage points, so take each measurement two or three times and use the average.

• Neck: measure just below the larynx (Adam’s apple), tape sloping slightly downward at the front.
• Waist (men): measure at the navel, standing relaxed, not after inhaling or flexing.
• Waist (women): measure at the narrowest point, usually just above the belly button.
• Hip (women only): measure around the widest part of the hips and buttocks.
• Height: measure barefoot, standing straight against a wall.

Healthy body-fat ranges differ meaningfully between men and women because women naturally carry more essential fat to support reproductive hormone function.

• Essential fat: Men 2–5%, Women 10–13%
• Athletes: Men 6–13%, Women 14–20%
• Fitness: Men 14–17%, Women 21–24%
• Average: Men 18–24%, Women 25–31%
• Above average (obese range): Men 25%+, Women 32%+

These bands are general reference ranges popularised by organisations like the American Council on Exercise; individual healthy ranges can vary with age and sport.

The Navy tape method typically estimates body fat within about 3–4 percentage points of more precise methods like DEXA scans or hydrostatic weighing for most people, which is accurate enough for tracking progress over time even though it is not lab-grade precision.

Very lean, very heavy, or unusually shaped bodies (for example, athletes with a very muscular neck or waist relative to height) can push the formula’s accuracy lower. Use the same tape, the same landmarks, and the same time of day each time you measure so that changes reflect real body composition shifts rather than measurement noise.

No single body-fat measurement, from any method, should be treated as gospel. The real value of a body-fat estimate comes from measuring consistently — same tape, same landmarks, same rough time of day — every two to four weeks, and watching the trend rather than reacting to any one number.

Pairing body-fat trend data with a tape measurement of your waist alone, progress photos taken under similar lighting, and how your clothes fit gives a fuller picture than any formula in isolation. Strength gains alongside a falling or stable body-fat percentage are usually a good sign that you are building muscle while managing fat mass effectively.

BMI alone cannot separate muscle from fat, so many people use the BMI Calculator as a quick population-style screen and this Body Fat Calculator when composition matters more. The Ideal Weight Calculator and Calorie Calculator then help translate a composition goal into a height-based reference range and a daily energy target.

This tool is for general screening and education only. It is not a medical device and does not replace advice from a doctor, dietitian, or other qualified health professional — especially if you are pregnant, under 18, managing a chronic condition, or taking medication that affects weight or metabolism.