A charming fuchsia pink hat of light thick-and-thin wool with a pattern of lavender flowers and pale green leaves. Child's size 2-5. You can roll up the brim to make it smaller, and it should fit for a long time. Not moth-proofed. Hand washable. Medium weight, not for really cold weather. This yarn is stretchier than most of the yarn I use, therefore I think this hat will fit longer. It will stretch about an inch.
Check the wikipedia article "hat" for size comparisons, conversion to metric, etc. The graph is at the end of the article.
inside circumference: 19.5 in /49.6 cm