My toddler is 15 months old. His head measures around 45th percentile for his age. Based on what I could decipher from a previous review, I ordered this hat in the 18-24 month size. It fits with room to grow. We are experiencing a winter-like spring, so this is perfect. His little red candy stripe hat covers his head down to the brows, nape, and well over both ears. I am a happy customer.