Body Fat Calculator
Estimate your body fat percentage using the U.S. Navy method.
Estimate using tape measurements; not a substitute for a body composition scan.
How the Body Fat Calculator Works
This calculator estimates your body fat percentage using the U.S. Navy circumference method, a practical technique that needs only a tape measure rather than special equipment. It relies on the relationship between where you carry circumference (especially around the waist and neck) and your overall body composition.
For men, the method uses height, neck, and waist measurements. For women, it adds the hip measurement, because fat distribution patterns differ. The calculator then applies a validated logarithmic formula to convert those measurements into an estimated percentage of body fat.
Body fat percentage can be a more informative number than weight alone, because it distinguishes lean mass (muscle, bone, organs, water) from fat mass. Two people at the same weight can have very different body compositions and health profiles.
How to Measure Correctly
Accurate measurements matter, since small tape errors change the result. Use a flexible tape, keep it snug but not compressing the skin, and measure on bare skin where possible.
- Neck: just below the larynx, with the tape sloping slightly downward to the front.
- Waist: for men, at the navel; for women, at the narrowest point of the midsection.
- Hip (women): around the widest part of the buttocks.
- Height: standing straight without shoes.
Take each measurement two or three times and use the average. Measure at a consistent time of day, ideally in the morning, for the most repeatable results.
The Formula and a Worked Example
The U.S. Navy method uses these formulas (measurements in centimetres):
- Men: 495 / (1.0324 − 0.19077 × log10(waist − neck) + 0.15456 × log10(height)) − 450
- Women: 495 / (1.29579 − 0.35004 × log10(waist + hip − neck) + 0.22100 × log10(height)) − 450
As an example, take a man who is 180 cm tall with a 38 cm neck and a 90 cm waist. The waist-minus-neck value is 52 cm. Plugging these into the formula yields an estimated body fat of roughly 18 to 19 percent, which falls in a typical, healthy range for many adult men.
The calculator performs this arithmetic for you, so you only need to enter accurate measurements.
Understanding Body Fat Categories
General reference ranges for body fat percentage differ by sex because women naturally carry more essential fat:
- Women: essential 10–13%, athletes 14–20%, fitness 21–24%, acceptable 25–31%, higher above 32%.
- Men: essential 2–5%, athletes 6–13%, fitness 14–17%, acceptable 18–24%, higher above 25%.
These bands are general guides, not strict diagnostic cutoffs. The Navy method is an estimate and can differ from lab techniques like DEXA scans or hydrostatic weighing by several percentage points, particularly at the extremes.
If you are tracking changes over time, consistency in how you measure matters more than the absolute number. For a precise assessment or advice about a healthy body composition for you, consult a healthcare professional or qualified fitness specialist.
Frequently Asked Questions
It is a reasonable estimate for most people and convenient because it needs only a tape measure, but it can differ from lab methods like DEXA by a few percentage points. Accuracy depends heavily on consistent, careful measuring. Use it best for tracking trends rather than as an exact clinical value.
Men and women store fat differently, so the formulas were developed separately. The female equation includes the hip measurement to better capture typical fat distribution, while the male equation relies on neck and waist. Using the correct formula for your sex improves the estimate.
It varies by sex and goals. Broadly, acceptable ranges are around 18–24% for men and 25–31% for women, with athletic ranges lower. Some fat is essential for health. For personalized targets, speak with a healthcare provider, since context and overall health matter more than one number.
Use a flexible tape, keep it snug without compressing the skin, and measure on bare skin at consistent body landmarks. Take each measurement a few times and average them, and measure at the same time of day, ideally the morning, to reduce day-to-day variation.
Body fat percentage distinguishes fat from lean mass, so it can be more informative than BMI, which uses only height and weight. However, both are estimates with limitations. Looking at them together, alongside measurements like waist circumference, gives a fuller view of your health.
No single estimate should drive medical decisions. This calculator is an educational tool to help you understand and track body composition. For diagnosis, health risk assessment, or a tailored plan, consult a doctor or qualified professional who can use validated methods.