Learning how to measure body fat takes nothing more than a tape measure. The calculator below uses the “U.S. Navy” method (based on measuring various body circumferences) to estimate your body fat percentage from a few measurements you can take yourself in about two minutes. Simply enter your height and the required measurements, and the calculator will determine the estimated percentage and the corresponding category.
How to Measure Body Fat With a Tape
The U.S. Navy method for determining body fat percentage based on circumference measurements relies on a simple observation: fat is not distributed evenly. In men, it accumulates primarily in the abdomen, whereas in women, it concentrates in the midsection and hips. By comparing these measurements against a reference value—such as neck circumference—and factoring in height, it is possible to arrive at a reasonable estimate of body fat percentage.
No special equipment is required other than a tape measure; consequently, this method is used by the Navy, in gyms, and by this calculator. Although a DEXA scan yields more precise results, it involves a fee and requires an appointment. In contrast, a tape measure costs very little and can easily be used in the comfort of one’s own bathroom.
How to Measure Your Waist, Neck and Hips
- Waist circumference: for men, at the level of the navel; for women, at the narrowest part of the torso. Since this measurement has the greatest influence on the result, it is important to determine it accurately.
- Neck: just below the Adam’s apple; the tape should be slightly angled downwards at the front.
- Hips: for women only; measure at the widest point, with feet together.
- Height: measure without shoes.
Hold the tape flat against the body without compressing the skin. Exhale normally before taking the measurement, rather than holding your breath or sucking in your stomach. Measure to the nearest half-centimeter and take each measurement twice; if there is a discrepancy between the values, take a third measurement and use the average.
What You Need to Enter
- Male / Female: the two formulas differ; the formula for women takes hip circumference into account.
- Height: in centimeters.
- Neck circumference: in centimeters.
- Waist circumference: in centimeters.
- Hip circumference: only for the formula intended for women.
The U.S. Navy Formula
For men: %BF = 495 ÷ (1.0324 − 0.19077 × log10(waist − neck) + 0.15456 × log10(height)) − 450
For women: %BF = 495 ÷ (1.29579 − 0.35004 × log10(waist + hip − neck) + 0.22100 × log10(height)) − 450
For a man 170 cm tall, with a neck circumference of 38 cm and a waist circumference of 85 cm, the result is 17.8%, which is the calculator’s standard value. For a woman 165 cm tall, with a neck circumference of 32 cm, a waist circumference of 75 cm, and a hip circumference of 95 cm, the value is 27.4%. It should be noted that the same percentage falls into a different category depending on sex, as women have a higher proportion of essential body fat.
This is the same standard the U.S. Navy body fat calculator uses, applied across all branches of the U.S. armed forces; consequently, it is sometimes referred to as the army body fat calculation. The U.S. Department of Defense selected this body-measurement-based method because it requires no equipment other than a tape measure and can be performed anywhere.
Body Fat Percentage Categories
These are the reference values from the American Council on Exercise, identical to those shown in the calculator’s results section. These values are higher for women across all categories, as they require a greater amount of essential body fat for hormonal processes and reproductive function.
| Category | Men | Women |
|---|---|---|
| Essential fat | 2–5% | 10–13% |
| Athletic | 6–13% | 14–20% |
| Fitness | 14–17% | 21–24% |
| Average | 18–24% | 25–31% |
| Above average | 25%+ | 32%+ |
Essential fat represents the minimum level the body needs for hormone production, organ protection, and temperature regulation. If levels remain below this threshold for an extended period, hormonal and immune functions may be impaired.
How Accurate Is the Navy Method?
For most people, the result differs by only a few percentage points from that obtained via a DEXA scan; while this figure is significant enough for practical use, it cannot be considered absolutely precise. This method is least reliable at the extremes of the spectrum: measurement errors frequently occur with both very lean athletes and individuals with significant excess weight.
Three factors can influence the measurement without the body actually having changed: the placement of the tape measure, the tension applied while using it, and the time of day. Therefore, consistency in measurement is more important than the absolute value. If you always take the measurement in the same way, the changes observed between readings will provide more insight than a single, isolated result.
Frequently Asked Questions
How do you measure body fat at home?
Use a tape measure. Measure your height as well as your neck and waist circumferences—adding hip circumference for women—and enter these values into the calculator above. The U.S. Navy formula calculates your estimated body fat percentage based on these measurements.
Where exactly do I measure my waist?
Men should take the measurement at navel level. Women should take it at the narrowest part of the torso, generally just above the navel. Exhale normally to start, and ensure the measuring tape stays level around the body.
Is the Navy method accurate?
For individuals who fall within the average range, the result generally differs by only a few percentage points from that obtained via a DEXA scan. The method is less reliable for very thin or very large individuals; furthermore, it does not allow for the localization of internal body fat.
What is a good body fat percentage?
The American Council on Exercise places the range corresponding to good physical fitness between 14% and 17% for men and between 21% and 24% for women, while average values fall between 18% and 24% and between 25% and 31%, respectively. These are descriptive categories rather than individual goals.
Why do men and women use different formulas?
Women store fat differently and have a higher proportion of essential fat; therefore, the formula designed for women also takes hip circumference into account and uses different coefficients. Applying the formula for men to a woman yields a meaningless result.
How is body fat different from BMI?
BMI only takes height and weight into account; therefore, it does not distinguish between muscle mass and fat mass. In contrast, body fat percentage provides direct information about body composition; consequently, a muscular person may appear overweight according to BMI, even though they have a low body fat percentage.
Related Calculators
- BMI Calculator — the height-and-weight screening number, and why it differs from this one.
- Calorie TDEE Calculator — daily energy expenditure.
- Percentage Calculator — for working with percentages generally.
- Age Calculator — body composition norms shift with age.
- Date Difference Calculator — track intervals between measurements.