Answer:
The tallest dog is the Irish Wolfhound. It can be up to 35 inches (89 cm). The larger Irish Wolfhounds are the size of a small horse.
The "biggest breed" is probably the English Mastiff, with males up to 240 lbs. (109 kg). The Neapolitan Mastiff and Newfoundlands are also very large adult dogs.
Also, dogs such as the Labrador Retriever can weigh up to 120 lbs (54 kg) Big breeds are just that "big." How big an individual dog gets depends on the breed, the size of its parents, and its diet. Dogs such as the Great Dane, the Alaskan Malamute, and the Saint Bernard can also grow to huge size; males reach 33-35 inches tall and weighs up to 115 kg.