My son is 10 years old, 4ft (on the more short side compared to friends), and I always buy him medium (8-10) in clothes. I was worried to size up, because of his height, but I'm happy I did, because it fits perfect.I love how the jacket can be worn any time, not just as a halloween costume, like we bought it for. My son loves it, we love it, and I think it is worth the money.See full review