5Y in kids is equivalent to a women's size 5. It typically corresponds to children who are between 8 and 9 years old, though some brands may vary slightly on the age range. To get an accurate fit, it is important to measure your child's foot length in inches or centimeters and compare that measurement with the brand-specific sizing chart for kids shoes. For example, Nike sizes 5Y as 19 cm while Adidas sizes it at 18 cm.