Weight for Age

Weight for Age (WFA) is a term in thoroughbred horse racing which is one of the conditions for a race. It means that a horse will carry a set weight in accordance with the Weight for Age Scale. This weight varies depending on the horse's age, its sex, the race distance and the month of the year. Weight for age races are usually Group 1 races, races of the highest quality.

WFA is a method of trying to equal out the physical progress which the average thoroughbred racehorse makes as it matures. The thoroughbred matures extremely quickly compared to the human being. By the age of two the horse has achieved 95% of its mature height and weight, and by the end of its third year it will be fully mature. To allow for this variation in maturity in the context of racing, it is necessary to express it as a function of the weight a horse will carry in a race. It is also necessary to take into account the race distance because stamina comes with maturity, and younger horses are at a greater disadvantage the further they have to run. If no allowance was made, a mature older horse would always beat a younger one.

The principle of WFA was developed by Admiral Rous, a handicapper with the English Jockey Club. Rous experimented with weights until he arrived at a relationship between age and maturity, expressed in terms of weight. His original scale has undergone only minor alterations since his work in the 1860s.