Toy: The dogs that fit into the category of Toy Breeds will vary depending on the Kennel Club. The AKC (American Kennel Club) is the largest and most recognized in the United States. They maintain a registry for purebred dogs only. Size is the main element which will determine if a dog is to be classified as a toy breed. Per the AKC, the Chihuahua is the smallest toy breed at an adult weight of 2-6- lbs. (.9 kg-2.7 kg) and the Pug is the largest at a full grown weight between 13-20 pounds (6-9 kg).
Small: There is not an official Small Breed Dog Group. Rather, certain dogs of a smaller size are unofficially classified with this term. These dogs may be officially classified as as Non-Sporting, Hound, Terrier or in the Miscellaneous group. Generally, the definition of a small breed dog is one who's standard weight is over 20 lbs. (9.07 kg) and under 30 lbs. (13.6 kg). For example the Besenji falls between 22-24 pounds (9.97 - 10.88 kg). Other small breeds dog do not have an official weight; however do have a standard height range.