The shoe size of a four-year-old girl fluctuates according to how quickly she is developing, but the average is a size 10 for children. Four is also the last age at which boys’ and girls’ feet are roughly the same size.
Generally, a girl’s feet continue to grow until around the age of fifteen, at which point they achieve their final size. Typically, girls grow approximately one and a half shoe sizes per year. When a girl is three, her shoe size is often a child’s size 9 or 9 1/2, and by the time she is five, it is typically a child’s size 11 or 12.