My kid was adorable at a family wedding. This does run large. At 16 months, my son wore the 12 month size needing about an inch hem on the pants. My son is skinny so 12 months still tend to fit him width wise, but he is long grown out of 12 month pants. Luckily we tried this brand on at a local store that did not carry the tux so knew what size to get him.