The vast majority of dogs in the United States have no verifiable lineage and you may not be able to determine what kind of pitbull you have by looking at it.
A pitbull isn't actually a specific kind of dog. There are several different breeds of pitbulls, each with distinctive characteristics. Knowing what kind you have may help you better understand your pet's needs and temperament. Physical characteristics are the best way to tell one type of pitbull from another. Once you know what kind of pitbull you have, make training decisions based on the breed. Where one breed is friendly, another needs a strong owner to show control.
Weigh your pitbull. Pitbull breeds vary greatly in size. The Staffordshire Bull Terrier usually weighs between 28 and 38 pounds, whereas the American Pitbull Terrier is between 35 and 65 pounds and the American Staffordshire Terrier is between 65 and 90 pounds.
Examine the head of your pitbull. If it has a very porportionate head, it might be an American Pitbull Terrier. Staffordshire Bull Terriers, on the other hand, are known for having very broad heads, according to the Pit Bull Info and Training website.
Don't depend on the length of the fur to tell you what kind of pitbull you have. Pitbulls are a short-haired dog that come in a variety of colors.
Ask your veterinarian what kind of pitbull you have. He may not know, but he should know where to find out.
Check any papers that came with your pitbull. The exact breed might be noted on the pedigree paperwork.