On average, dogs run about 19 miles per hour. Although breeds vary tremendously, many types of dogs run much faster. Greyhounds run 45 miles per hour, and the Saluki runs even faster in short, 1/2 mile distances. For short bursts, many dogs can exceed 35 miles per hour.
Speed and size are relative, for dogs and other animals. For example, the actual running speed of a house mouse is only about 8 mph; but if that mouse were the size of a man, its speed would be nearly 160 mph. A giraffe can run at a top speed of over 32 mph; but if a giraffe were the size of man, its top speed would only be about 11 mph.