📏 Body Fat Calculator
You do not need calipers or a lab to estimate body fat. The U.S. Navy method uses a tape measure around your neck, waist (and hips for women) plus your height, and its logarithmic formula lands surprisingly close to lab measurements for most people.
Measure in the morning, keep the tape snug but not tight, and re-measure monthly — the trend matters far more than any single reading.
How to use this calculator
Choose your gender, enter your height and neck and waist measurements (plus hips for women), and the tool estimates your body fat percentage with the U.S. Navy method.
- Select your Gender from the dropdown.
- Enter your Height in centimetres.
- Measure and enter your Neck circumference and Waist circumference, taken at the navel.
- Women also enter Hip circumference, then read the body fat percentage and category.
Frequently asked questions
What does this calculator compute and what are the inputs?
It estimates the share of your body that is fat tissue, shown as a percentage with a category like Athletic, Fit or Average. Inputs are height and a few tape-measure readings: neck and waist for men, neck, waist and hips for women.
What method does it use?
The U.S. Navy circumference method, a set of logarithmic formulas developed from military body-composition research. It compares the waist (and hips for women) against the neck and height to separate lean mass from fat mass.
Can you show a worked example?
A man 175 cm tall with a 38 cm neck and an 85 cm waist scores about 23.5% body fat, which sits in the average band for men. Drop the waist to 78 cm with the same neck and height and the result falls to roughly 18%, in the fit range.
How reliable is a tape-measure estimate?
For most people it lands within a few percentage points of lab tests, though it can mislead for very muscular or very lean builds. Measure in the morning with a snug-but-not-tight tape and follow the trend month to month rather than obsessing over a single number.