Body Fat Calculator

How Body Fat Calculator works

Estimate body fat percentage from tape measurements with the US Navy formula: waist, neck and height, plus hip for women. Everything happens inside this page: the tool reads your input, runs the calculation or conversion locally, and hands the result back to you. Nothing is transmitted, because there is no backend to transmit it to.

That design choice is deliberate. Most free tool sites upload your files to a server, process them there, and quietly keep a copy. Toolcin cannot do that — the site is a set of static files. If your connection dropped the moment the page finished loading, every tool would still work.

The US Navy tape method

The formula uses waist, neck and height for men, and waist, hip, neck and height for women. It estimates body fat percentage from circumference, on the reasoning that waist size relative to neck and height tracks fat distribution.

Accuracy is typically within 3–4 percentage points of a DEXA scan — useful for tracking change over time, less useful as an absolute number.

Measuring consistently

Measure at the same time of day, on bare skin, with the tape snug but not compressing. Waist at the navel for men and at the narrowest point for women; neck below the larynx. A one-centimetre error moves the result by about one percentage point.

Reading the result

Essential fat is roughly 3% for men and 12% for women; athletic ranges are higher, and 25%+ (men) or 32%+ (women) is generally classed as obese. These are population bands, not personal targets.

Good to know

• Works offline once loaded, including on flights and in locked-down networks.
• No file size limit beyond your device's own memory.
• Free to use, with no account and no usage counter.
• Results are produced locally, so they are not logged or shared with anyone.

Questions

How this number is produced

The calculation is the US Navy circumference method using waist, neck and height (plus hip for women), following US Navy body-fat estimation. The formula is repeated here so the result can be checked by hand rather than taken on trust.

This is a calculator, not advice. No clinician, accountant or adviser has reviewed it, and it cannot see your circumstances. For anything involving health, a loan, a tax filing or a religious obligation, confirm the figure with a qualified professional or the authority that publishes the rule.