Every gymnast is different. Some have petite figures with delicate short arms and legs, while others stand tall and flaunt their graceful elongated bodies. As everybody is unique, so are measurements.
It's amazing how large of a role body proportions play in choosing the right size. A gymnast can have either a long or short torso body type, but they can also have narrow shoulders and a wide waist, which means they don't fit into a specific size.
That's where girth comes in. The girth is the measurement that goes from the top of the shoulder, then between the legs, and finishes back at the top of the shoulder. It essentially measures how long your torso is. So if you're ordering your gymnastics leotard the torso measurement should be the deciding factor.