Harper is 10 years old and wears size 10-11Y. If you prefer a super oversized hoodie look you can size up for that extra long look.
Garment measurements by size (approx):

Size (cm) 1Y 2-3Y 4-5Y 6-7Y 8-9Y 10-11Y 12-13Y
Chest 41 46 49 52 55 58 61
Length 36 42 46 50 54 58 62