My grandson wears a size 3T. So, I ordered a 3T and it fit him perfectly! If I used the measurement guide, it said to order a 2T which would have been too small. I am not sure if I measured him correctly, though. This outfit is very good quality and is comfortable. it has a silver vest, short sleeved white shirt, light blue tie that comes tied and is a loop around the neck which you just pull to size (not a clip tie) so it stays on. the silver shorts have elastic. This is nice enough to wear to a wedding. Do not hesitate to buy this for a fancy event. Our Baptism was in a church with a home party and it was perfect for this event as well. I write this because I always look at reviews before I make a purchase and I want to assure you that this is a good purchase. I paid extra to have it delivered within 2 days as the Baptism was in 5 days of ordering and I didn't want to chance it not being delivered on time. It came just as promised and was beautifully packaged so I didn't have to iron it and he wore it straight from the package.