Horses must be three years old to race in the Kentucky Derby. This age requirement applies to all Thoroughbreds competing in the race, which is held annually on the first Saturday in May. The rule ensures that all horses have reached a similar stage of physical and mental maturity to handle the demands of the race, which covers a distance of 1ΒΌ miles (10 furlongs) at Churchill Downs in Louisville, Kentucky
. In Thoroughbred racing, all horses officially have their birthday set as January 1 of the year they were born, regardless of their actual foaling date. This standardization means that horses competing in a given year's Derby are all considered to be the same age-three years old-even if some may be physically younger by several months. This system helps level the playing field but also means horses born earlier in the year may have a developmental advantage
. No exceptions to the three-year-old age rule exist for Derby eligibility, making it a strict and longstanding standard in the sport
. Most horses begin training and racing as two-year-olds to prepare for this major event
