Teacup dogs are not recognized by any major breed classification organization, so there are no precise specifications for what classifies a dog as a teacup. Dogs are usually classified as teacup when they are bred to be 2 - 5 pounds in weight at full adulthood, and under 17 inches in length. The term “teacup” was coined because, at birth, these dogs manage to get comfortable inside a teacup. The term denotes their tiny size, and doesn’t refer to a dog’s pedigree or breed.