According to the search results, a 24-inch bike is typically the best fit for kids aged 8 to 13 years old. However, the age range for a 24-inch bike can vary depending on the childs height and inseam. Kids on 24-inch bikes are generally confident enough riders to set their seat about 2 – 3″ above the child’s inseam, which produces the best knee bend angle for pedaling with maximum efficiency. The height adjustability of 24-inch bikes ranges from 5″ – 8″, which allows kids to ride 24-inch bikes for a few years.