Body Fat Calculator
Estimate body fat percentage from the U.S. Navy tape-measure method and see estimated fat mass and lean mass. Browser-only.
Results
Body fat calculator: the tape-measure method
This calculator of body fat estimates the fat fraction of your body from circumference measurements, using the published U.S. Navy method. Enter your measurements in centimetres or inches and it returns an estimated body fat percentage, along with the fat mass and lean mass that percentage implies at your body weight.
What it needs depends on the equation for your sex:
| Equation | Measurements needed |
|---|---|
| Men | Height, neck and waist |
| Women | Height, neck, waist and hip |
It runs entirely in your browser, with no account and nothing stored.
How this estimate works
This page uses the published U.S. Navy circumference method. It converts the measurements to inches once, applies the sex-specific equation, then derives estimated fat mass and lean mass from the percentage and body weight you entered.
Both equations read the circumference term against height on a logarithmic scale, which is why a small tape error does not translate into a proportional error in the answer, and why the method behaves differently at different heights.
What can move the result
Tape placement, breathing, posture, and how tightly the tape is held can change the estimate by several percentage points. Pregnancy, high muscularity, and non-standard fat distribution can also make the method less suitable.
If you intend to track change over time, consistency matters more than any single reading: the same tape, the same landmarks, the same time of day. A difference between two readings taken differently is not a change in body composition.
Sources and limitations
Sources reviewed 27 August 2026. This is an educational tape-measure estimate for healthy adults and not medical advice or a diagnosis.
This page deliberately reports no healthy or target body-fat range. Published ranges vary by source, sex, age and athletic population, and the calculator does not model any of that, so naming a target it cannot support would be false precision. For a weight-against-height screening measure instead, use the BMI calculator.
Frequently asked questions
Is this a clinical body-composition test?
No. It is a tape-measure estimate using the published U.S. Navy circumference method, and small measurement differences can move the result materially.
How do you calculate body fat with a tape measure?
The U.S. Navy method uses circumferences and height. For men it works from the difference between waist and neck; for women it works from waist plus hip minus neck. Both are read against height on a logarithmic scale. This calculator of body fat does that arithmetic once your measurements are entered, in either centimetres or inches.
How accurate is this body fat calculator?
It is an estimate from three or four tape measurements, so it is far less precise than DEXA, hydrostatic weighing or air-displacement methods. Tape placement alone can move the result by several percentage points, which is why the page treats it as a screening estimate rather than a measurement.
How do I measure accurately?
Measure on bare skin, keep the tape level and snug without compressing, breathe normally and measure at the same point in the breath each time. Take each measurement more than once and use a consistent time of day. Repeatability matters more than any single reading if you intend to track change.
What are fat mass and lean mass?
Fat mass is your body weight multiplied by the estimated percentage; lean mass is what remains, which includes muscle, bone, organs and water. Both are derived from the percentage and the weight you entered, so both inherit whatever error the percentage carries.
How is this different from BMI?
BMI is weight against height squared and does not attempt to separate fat from anything else. This method estimates the fat fraction specifically, from circumferences. They answer different questions, and neither is a diagnosis.