Order a size larger than what you measure at or measure over thick clothes. My son wears 2T but I measured him around the waist (under clothes) and he was 20.5 so went with size Small or 3T. I shouldve listened to the reviews that said order larger but I thought I already was going from 2T to 3T. Its almost too small over his jeans. I just got this today so Im not sure how well it will hold up. I may even exchange it for a medium. We will see when he lets me put it on him tomorrow. Other than sizing, this seems like a great belt.