Real World Sizing Examples:
My 5 and 1/2 year old son is a 50th percentile kind of kid. He fits great in the 6 as well as the 8. The 6 is a perfect fit while the 8 is a looser look on him. My 2 year old son fits great into the size 2 and has done since he was about one and a half. These are 100% cotton shirts so some shrinkage is normal after the first few washes.