I bought these same socks when my daughter was an Infant & and we loved them! so whenshe needed more socks now at 21 months I was so excited to see they offered larger sizes. I bought the 18-36 months & hoped they would fit. Since there really isn't any size guide available.

My daughter wears a shoe size of Toddler 7.5 or 8. The 18-36 months sized socks fit her PERFECTLY! They are not tight and she has a tiny bit more room for her feet to be longer. the cuff is not tight around her calves.

She is an average to thin size. She is 32.5 inches tall and 30lbs.

I hope this helps someone in their purchase.