To assess the racing class and potential value of a horse and its offspring, a rating calculation system is employed. The more races a horse has won and the more prestigious prizes it has claimed, the higher its class and rating.
To minimise subjectivity in assessing a horse's class, the rating is calculated and presented in a digital format, providing clarity and convenience. Horses participating in racing are never equal in strength; variations in speed, endurance, and nervous system stability are inevitable. To level the chances of winning, a conditional weight that a horse can carry was introduced. The stronger the horse, the more weight it can carry (or actually carries in a handicap race), resulting in a higher OR rating. Conversely, a weaker horse carries less weight and is rated lower.
The maximum 100% conditional load on a horse is 140 pounds, also representing the maximum rating value. A horse receives its initial rating after participating in a starter or maiden race (horses starting for the first time or without victories). To qualify, the horse must win or finish among the first six. Subsequently, the OR rating is adjusted based on its racing success or failure.
Calculating the rating is intricate; in addition to the conditional weight, factors such as the horse's weight, race result, racetrack, distance, track surface, and draw results are considered. Complex mathematical formulas yield a comparative assessment as close as possible to reality. The level of competition influences the rating, with stronger competition and higher ratings adding more points to the evaluated horse's rating. Subjective factors, like a horse making a late surge despite losing, may lead judges to add points to its rating.
To participate in races of 1st-grade stake races, the horse's rating must be no lower than 115; for 2nd-grade races, the rating should be no lower than 110, and so on. The requirements for the ratings of horses competing in races of 2, 3, and lower classes are reduced accordingly. The rating system is convenient because it allows a quick assignment of a horse to the desired race class by assessing its performance, each class having its own range.
Sports data provider Timeform ranks the world's top racehorses, with the highest rating in the world so far being 147 for the unique horse Frankel. Frankel won all 14 races in which he participated, with 10 of them being races of the highest class.
Under the auspices of the International Federation of Equestrian Sports (IFHA), the world rankings of the best horses are also maintained by the Swiss watch manufacturer Longines. The results of the most significant horse races in North and South America, Europe and Asia, the Middle East, Australia, and New Zealand serve as the basis for compiling the ratings. To be included in the Longines World's Best Racehorse Rankings, a horse must have a rating of at least 115. At the end of the year, the highest-scoring Horse of the Year is determined. According to Longines, the rating of Frankel, the best horse of 2012, was 140, and this record remains unbroken until recently.
On January 23, 2024, the 2023 edition of the World's Best Racehorse Rankings was released. The Horse of the Year was Equinox, a Japanese stallion born in 2019, with a rating of 135. The rating of 128 was shared by Irish horses Ice Impact and Mostahdaf. The offspring of highly rated horses are used to improve the purebred breed; at auctions, such foals cost a lot of money. Usually, they justify their pedigree, recouping the money invested and becoming first-class horses.