The decades-old test is simple to perform. If a service member exceeds recommended weight limits, a measuring tape is used to measure their neck and waist for males, and neck, waist and hips for females. Those measurements are compared to their height to estimate the percentage of body fat they are carrying.

Moving forward the test will be confined to measuring a soldier’s waist, regardless of gender. If a soldier exceeds the body-fat allowance to serve but they score a 540 in the Army Combat Fitness Test with at least 80 points across each event they can waive the body-fat test, Army Times explains.

After a review of the test, the army reportedly determined it to be accurate enough to continue using, rather than investing in more expensive — and more accurate — methods of testing. Measuring tape costs about $5 while body-scanning equipment and X-ray machines cost between $10,000 and $100,000.

The U.S. Army Research Institute of Environmental Medicine performed the study of the tape test’s accuracy, observing data from 1,801 men and 889 women in the service. Researchers found 90% who were measured first by height and weight surpassed weight limits, thus requiring a tape test, according to Army Times. They also found that the tape test is more accurate when limited to a measure of the waist alone.

The institute said the tape test gives results within 2 to 3% accuracy, while other methods are within 1% or less.