Horses on average can run at approximately 30 miles per hour. It must be noted that there are several factors that can affect the running, or galloping speed of a horse. These include the size of the horse, its body structure, conditioning, athletic ability and the length of its stride.
Horses uses several gaits when moving forward and these are the walk, the trot, the canter (or lope) and the gallop. The gallop is a horse's fastest and more ground-covering gait and it is often used by horses in the wild to flee from a perceived threat. At full speed, a horse will gallop for about 1 to 2 miles before they stop to take a rest. At a slower gallop, horses may be able to cover a longer distances before stopping or slowing down to rest.
Some horses are specifically bred to gallop fast, particularly thoroughbred and quarter horses. Thoroughbreds are known to register speeds of up to 40 miles per hour during races. Quarter horses, which are bred and trained to run short and quicker distances, can clock up to 50 mile-per-hour speeds.
The fastest speed ever recorded for a race horse was 43.97. This was achieved a racehorse named Winning Brew at the Penn National Race Course in Grantsville, Pennsylvania in 2008. The 2-year old filly thoroughbred, which was trained by American Francis Vitale, was able to cover the quarter mile race track in 20.57 seconds.