Children's shoe sizes are typically measured in a numerical system that varies by region. In the United States, sizes usually range from 0 to 13 for infants and toddlers, followed by youth sizes from 1 to 7. Each size increment generally corresponds to about one-third of an inch in length. Sizing can differ between brands, so it's important to try shoes on for the best fit. Additionally, children's feet grow quickly, often requiring new shoes every few months. Regularly checking the fit can help ensure comfort and support for activities like running and playing.