Our youngest is a year and some change, and she isn’t huge by any means, but we have found that the 3T fit her well. They are very slightly long in the legs, but they also seem to have quite a bit of stretch to them, so I think they will last is a while with her.For reference she is very much average height, but she is 30lbs at just over a year. So I wouldn’t say that the 3T is too big for her. A 2T might have fit ok, but I didn’t want to pop any seams like we have with other pjs.I will say thouSee full review