The generally agreed upon distinction between a horse and a pony is one of height: a horse is an equine at least 14.2 hands (4ft. 10 inches, or 147cm), and a pony is an equine under that height. This distinction is not entirely accurate, however, as there are exceptions where an animal under 14.2h would still be considered a horse, and conversely, where an animal over 14.2h would still be considered a pony.

Ponies also usually share a number of characteristics aside from their smaller stature which identify them as ponies. Their frame is generally quite a bit stockier than that or a horse, with a specific confirmation type. They generally are much stronger, pound for pound, than horses. They tend to be hardier and more resistant to cold weather than horses. They also tend to be quite intelligent, and as a result can often be very stubborn.

Because of the secondary distinctions, there are a number of breeds which may tend to be less than 14.2h at maturity, but which most people would consider horses. Caspians and American Miniature Horses, for example, are both generally considered horses. The Caspian Horse, however, rarely exceeds 12h, even when full grown, and the American Miniature Horse cannot, by definition, be larger than 8h, but is still considered by breeders to be a true horse.

A similar example can be seen in the Icelandic horse, which rarely exceeds 14h when full grown. Many people refer to this breed as the Icelandic pony, and some DNA testing does seem to connect the breed to that of other pony breeds. Most breeders, however, consider the Icelandic horse to be a true horse, and it is a matter of some contention among enthusiasts. Despite the contention, Icelandic horses exhibit many of the characteristics of ponies: they have hardy coats, are intelligent, and virtually never reach a height of 14.2h. This case demonstrates that sometimes the only real distinction between a horse and a pony is a choice of word, often chosen for political or cultural reasons.

Many horse breeds may also show examples which are shorter than 14.2h, and in some cases may even have some other traits of ponies, but if the breed itself doesn’t meet the criteria, these are simply considered irregularities. Arabians, for example, may not uncommonly reach full maturity at 14h or 14.1h, but these are still considered genuine horses, and not ponies, because as a breed Arabians are solidly horses.

Within both pony breeds and horse breeds there is a great range of heights and features as well, which can complicate things somewhat. Horses can range from just under 14h, particularly riding horses such as Morgans or Arabians, to in excess of 20h in extreme cases. Similarly, there are horses that are incredibly strong, and horses which have developed hardy cold-weather features. In general, however, pony features will not be seen in great abundance in anything other than a pony breed.

It is important to recognize that the distinction between pony and horse is one that is judged at maturity, and based on the breed as a whole. Foals are usually less than 14.2h, but if they are of horse stock they will nearly always exceed that height by the time they grow up. People often confuse young horses for ponies, but ponies are strong, hardy animals, often capable of carrying riders or pulling ploughs, despite their small stature. They come from an entirely different stock, one that evolved on the frontiers of the horse world, developing features to help them survive in cold, harsh climates.