Boys' clothing sizes are determined by the child’s measurements. Finding the appropriately sized clothing for growing boys requires measuring the boy and finding out his real size. There are other considerations, such as slim or husky sizes, that can make it seem complicated, but sizing the boy makes it easier to buy clothes that fit.

Measure the boy around the waist to determine his waist size. Boys’ pant sizes are determined by the waist and hip measurements. Wrap the measuring tape around his waist, measuring in inches, and follow that by the hip. Hips are generally about 1 or 2 inches larger.

Get the height measurement to find out how tall the boy is. This will determine shirt and pant sizes when combined with other measurements. Measure height from the feet up to the top of the boy’s head.

Measure the chest size in inches. Chest size is the area under the arms, without the measurement of the arms and shoulders. Wrap the measuring tape under the arms and around the body.

Look at the sizing chart. The sizing chart tells sizes for boys' clothing based on the measurement in inches. For example, a boy that should wear 5S would measure 42 inches tall, 22.5 inches at the chest, 23 inches at the hip and 19.5 inches at the waist.