With so many dog breeds around, it can be confusing to try to figure out which is what when it comes to telling some of the similar breeds apart. One example of this complexity is the distinction between miniature and toy dogs. The two types are definitely distinct, but the details and the differences between one and the other vary by the specific breed of dog. In order to determine which category a dog falls into, it is usually necessary to look at the individual breed standards.
The American Kennel Club divides dogs into groups based on various temperamental characteristics, such as sporting, working and herding dogs. The club also recognizes a Toy Group, a group that in 2012 consisted of 21 different breeds. Some of these breeds may have larger varieties of the animal, such as the poodle, while others stand alone, such as the Chihuahua and the Maltese. The breeds that make up this group are the smallest dogs in the AKC, with some exceptions; and they generally do not have a limit on how small they can be -- only a restriction on maximum size.
Miniature dogs are generally larger than toy breeds but are smaller than standard-size dogs of the same breed. Each breed sets its own standards for how big a miniature should be. For example, a miniature Australian shepherd is between 14 inches and 18 inches tall while a miniature poodle is between 10 inches and 15 inches in height. Toy dogs are smaller than miniatures, and standard dogs are larger. In the Australian shepherd and poodle breeds, as with many others, the only distinction between the standard, miniature and toy varieties is the size.
A teacup dog of any breed is the smallest possible version of that dog. The American Kennel Club does not have a teacup category, but in most of the toy breeds a very small dog, usually one under 4 lbs., is called a teacup, though thats an informal designation. As an example, according to the AKC, the poodle exists in standard, miniature and toy sizes, but the description for toy poodles calls for any dog under 10 inches in height. That means that even the very tiny teacups qualify as toy poodles for show, registration and breeding purposes.
While many breeds base acceptable size on the height of a dog at the withers, this is not true of all breeds. Some types, such as the Chihuahua, specify a body type but do not place a limit on how tall the dog can be. Instead, breed standards for some dogs call for a weight limit, and dogs over that limit are disqualified from the show ring. In the case of the Chihuahua, for example, if a dogs weight is over 6 lbs. it cannot be shown.