Calculator · Body Fat Calculator
Calculate your body-fat percentage
The body-fat calculator gives a computed estimate of your body-fat percentage based on the selected method and the measurements you enter.
Result
- Body-fat percentage
- 15.3%
U.S. Navy estimate — robust orientation without a device.
The U.S. Navy circumference method is a prediction equation. Measurement position, body shape and the original target population affect error; there is no universal ±3 % guarantee for every individual.
Circumference-based body-fat estimate, not a reference measurement. Use it consistently within the same method and do not over-interpret small differences.
Method
How the calculation works
We use the U.S. Navy circumference method: a sex-specific formula estimates body fat from height, neck and waist circumference (women also include hip circumference).
A tape measure, calm breathing and the same posture each time are enough. Ideally measure in the morning, fasted, in the same state as your previous measurement.
Methodology: formulas, assumptions and estimate confidence →
Estimate confidence
How reliable is this estimate?
Low
The equation is deterministic, but individual model and measurement error can be substantial. No blanket ±3 % guarantee is claimed.
Interpretation
How to read your result
The result is a model-based estimate. Use the same measurement sites, tape and similar conditions when comparing values over time.
A trend can be practically useful, but it still contains measurement noise. A change in the number does not automatically equal the same change in actual fat mass.
Limits
Where this calculator ends
The U.S. Navy equations were developed for specific populations and measurement protocols. Body shape and deviations from the protocol can change individual error; a universal ±3 % accuracy claim does not follow from the equation.
DEXA, hydrostatic weighing, skinfolds, bioimpedance and circumference equations are different methods with different assumptions and error sources. Their results are not directly interchangeable.
Common mistakes
Common mistakes
- 01Treating the percentage as an exact measurement.
- 02Changing measurement sites or tape tension between sessions.
- 03Treating different body-fat methods as the same scale.
- 04Reading small fluctuations immediately as fat gain or loss.
- 05Deriving general health or aesthetic judgments from the result.
Example
A worked example
Illustrative tape-measure example
The equation produces a percentage from the entered circumferences. Repeat measurements under similar conditions and only interpret differences as a trend when they are reproducible.
FAQ
Frequently asked questions
- Is the calculated body-fat percentage exact?
- No. It is the output of a circumference equation and can differ from other reference or field methods in an individual.
- How can I measure more reproducibly?
- Use the same anatomical sites, similar tape tension and similar daily conditions. Repeated measures can help reveal obvious reading errors.
- Is DEXA perfect ground truth?
- DEXA is also a measurement method with its own assumptions and device/protocol effects. It should not be described as universally error-free ground truth for every field method.
- Which body-fat values are healthy or aesthetic?
- This calculator deliberately does not define them. Such judgments depend on the individual, context and goal and do not belong in a generic circumference equation.
- Can I compare different methods directly?
- Only cautiously. Different methods can produce systematic differences; consistency of method matters more for tracking.
Sources
Sources
More
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