Here is the size chart for selecting Orca wetsuits for kids. These wetsuits are determined based on age, chest, waist, hips, and height when finding the right size.
Usually, size selection is based on age, but the most critical measurements are waist and chest size. Ideally, a wetsuit should not fit too loosely. If there are many air pockets or 'bags' around the suit, it's too big for you.