There are 161 breeds officially recognized by the American Kennel Club -- and those probably do not cover many of the dogs you see at your local dog park. If you don't know the background of your mixed-breed dog, there are ways to figure out the likely breed of your dog's dam and sire. Identifying dog mixes is not an exact science -- although canine DNA testing is changing that -- and relies largely on the comparison of physical traits.
Purchase a breed book or find a website that has a list of dog breeds with pictures. You will need to visually identify common traits from several animals to get a clue about your dog. The American Kennel Club website has images and descriptions of the breeds it recognizes (see Resources).2
Weigh your dog. One of the most distinct differences between many dog breeds is size, so getting an idea of how big your dog is will help with identification.3
Look at identifiable physical traits such as ear shape and size, tail shape and size, body build, and length/shape of snout. Many dogs have personality or temperament traits that also can be compared.4
Compare your dog's strongest traits to your breed book or the dogs you see online. Use this information to make an educated guess as to what breeds of which your dog is a mix.