Body Fat Percentage Calculator
Estimate your body fat percentage from tape measurements using the US Navy circumference method, with an optional fat-mass and lean-mass breakdown when you add your weight.
US Navy circumference estimate
| Step | Value |
|---|---|
| Method | US Navy |
| Sex used for the calculation | Male |
| Measurement unit entered | Centimetres |
| Height | 180 cm |
| Neck circumference | 40 cm |
| Abdomen circumference | 92 cm |
| Formula measurement units | Inches |
| Estimated body-fat percentage | 19.9% |
View the formula
Body-fat % = 86.010 × log₁₀(abdomen − neck) − 70.041 × log₁₀(height) + 36.76
Body-fat % = 163.205 × log₁₀(waist + hip − neck) − 97.684 × log₁₀(height) − 78.387
Every dimension is converted to inches before the logarithms are taken. Age and weight are not part of this calculation.
This is an estimate, not a diagnosis. Tape-measure results vary with tape position, posture, breathing and body shape. Measure under similar conditions each time and focus on the change over weeks rather than a single reading. Estimated lean mass includes muscle, water, bone and organs — it is not a measure of muscle mass alone.
Not medical advice. The US Navy circumference method is a rough estimate from body measurements. It is not equivalent to a DEXA scan, hydrostatic weighing, a BodPod or a clinical assessment, and it does not measure health, fitness or appearance. Body-fat categories are broad reference ranges only.
What this calculator estimates
This tool gives an estimate of body fat percentage using the US Navy circumference method — also called the tape-measure method. It works from your height and a few body measurements. It is an estimate based on body circumferences, not a medical measurement, a diagnosis, or a direct measure of health, fitness or appearance.
If you add your current weight, it also estimates your fat mass and lean mass. Weight does not change the percentage itself.
How to use this calculator
- Choose the sex to use for the calculation — the formula and fields differ.
- Pick your measurement unit: centimetres or inches. It applies to every measurement.
- Enter your age. The calculator is for adults aged 18 to 120.
- Enter your height and neck circumference.
- For men, enter the abdomen circumference at navel level. For women, enter the natural waist and the hip circumference.
- Optionally add your current weight to also estimate fat mass and lean mass.
- Read your estimated body fat percentage, its reference category, and the breakdown.
Switching the measurement unit converts the values you have already entered.
How the US Navy body fat formula works
Every measurement is first converted to inches, then put through a sex-specific formula that takes the base-10 logarithm of a circumference difference and of height.
- All dimensions are in inches; centimetre input is divided by 2.54 first.
- The abdomen − neck (men) or waist + hip − neck (women) difference must be positive, or the formula has no answer.
- Age and body weight are not used.
Worked example. A man 180 cm tall, neck 40 cm, abdomen 92 cm. In inches that is height 70.87, neck 15.75, abdomen 36.22. Body-fat % = 86.010 × log₁₀(20.47) − 70.041 × log₁₀(70.87) + 36.76 ≈ 112.8 − 129.6 + 36.76 ≈ 19.9%, which falls in the typical reference range.
How to take each measurement
Use a flexible tape measure. Keep it level and snug against the skin without compressing it. Take each measurement twice and average them if the readings differ.
- Height — stand tall, without shoes.
- Neck — measure around the neck just below the larynx, roughly just below the Adam's apple, keeping the tape level rather than sloping.
- Abdomen (men) — measure horizontally around the abdomen at navel level. Stand relaxed and breathe normally; do not pull your stomach in.
- Natural waist (women) — measure around the narrowest part of the torso, usually just above the navel.
- Hips (women) — stand with your feet together and measure around the widest part of the hips and buttocks.
How fat mass and lean mass are estimated
- Shown only when you enter a weight; otherwise this section is hidden.
- Lean mass here is all non-fat tissue — muscle, water, bone and organs — not muscle mass alone.
What the body fat categories mean
These are broad reference ranges for context only. They are not a diagnosis, a health or appearance assessment, or a target. Body fat percentage alone does not define health or fitness.
| Category | Women | Men |
|---|---|---|
| Essential fat | 10–13% | 2–5% |
| Athlete range | 14–20% | 6–13% |
| Fitness range | 21–24% | 14–17% |
| Typical range | 25–31% | 18–24% |
| Higher range | 32% and above | 25% and above |
Limitations of the tape-measure method
- It is an estimate. Results vary with tape position, tape tension, posture, breathing and body shape.
- It can be several percentage points out for very lean or very muscular people, and for body shapes far from those in the original sample.
- It is not equivalent to a DEXA scan, hydrostatic weighing, a BodPod or a clinical bioelectrical impedance assessment.
- It is for adults. It does not assess health conditions and is not medical advice.
- For a useful comparison, measure under the same conditions each time and watch the trend over weeks rather than a single reading.
To compare this with a height-and-weight screen, use the BMI calculator, or estimate your daily energy needs with the maintenance calories calculator.