Soccer ball sizes typically are determined by the age of the players. U.S. Youth Soccer issues guidelines for soccer ball sizes in competition for youth age groups, though individual leagues may have their own rules. In addition, players sometimes use different sized soccer balls for training purposes. For instance, some seasoned players use a size one ball, which is the smallest sized soccer ball, to practice skills. The size one ball may also be useful for the youngest players learning the sport.
For adult players, such as those at the collegiate, professional and international levels, the size five ball is standard for competitive play. The size five ball has a circumference of 27-28 inches and a weight of 14-16 ounces. U.S. Youth Soccer also recommends the size five ball for youth players in the age 13-and-under age category and older. Size four soccer balls, which have a circumference of 25-26 inches and a weight of 11-13 ounces, are recommended for players in the under-12, under-11 and under-10 age categories. Players younger than that are advised to use the size three soccer ball, which is 23-24 inches and 11-12 ounces.