My children are 40 inches tall and weigh 36 pounds. I bought a size 4-6 for my 5 who just turned 5 and she ran out. It fits them like low-cut jeans, and when they wear short socks, there's a strip of bare skin between the sock and the pants that's visible when they go out to play in the cold. The pants also roll up when children walk and run, and need regular tightening and stretching after walking for a few minutes. Thick, warm and comfortable, they're better than Gap's winter pants. Next time I will order a size for 6-8 years.