Question: How big does a dog need to be to be considered a giant breed?

Giant dog breed


A giant dog breed has no universal height or weight classification, although some groups define "giant breeds" as those heavier than 50 kilograms (110lb). Giant breeds grow rapidly, but take longer to mature into their full adult sizes than smaller dogs.[1]
Advantages and disadvantages
Many giant breeds are mature, soft and relaxed dogs as adults and require less exercise than most smaller dogs, so they can make better pets for small living arrangements, such as apartments. Because they are larger animals, they are less likely to be intimidated by other people and thus are much more adaptable to meeting friends, family members, and children of owners.  They are normally very calm and are great family dogs. If they sense a threat towards their owner, they will become very protective. They are, in general, stronger than other breeds and many giant breeds are well known for their working abilities.[2]
Giant breeds often have health-related disadvantages when compared to smaller dogs and caring for them is usually more expensive than for smaller dogs.[2]  They eat more than smaller breeds and sometimes require speciality diets to tackle weight and joint management.[3]
In addition to spending more on food, expenses overall may be more than for most breeds. Larger beds, collars, and toys cost more, as do grooming and kenneling very large dogs. There is also the issue of more expensive veterinary bills. For instance, anaesthetics and pharmaceuticals are charged by volume/mass, which is determined by the weight of the dog.  Joint problems, such as hip dysplasia and arthritis, are common.[1] Large breeds are also quite prone to osteosarcoma and susceptible to other debilitating bone and cartilage diseases. This is the result of a much higher growth factor—adult weight versus birth weight—and much longer growth period.[4]  Their life span is generally shorter than that of smaller dogs, often living only 6 to 10 years.
Notable giant dogs
Giant George was a blue Great Dane previously recognised as the world's tallest living dog, and the tallest dog ever by Guinness World Records.
Titan was an American male white Great Dane who was a holder of the Guinness World Records as the world's tallest dog.
Zeus was a Great Dane from Otsego, Michigan, United States, famous for being named the world's tallest dog for the 2012 and 2013 Guinness Book of World Records.
Zorba, an English Mastiff from the United Kingdom, weighed in 1989: 343lbs (155.6kg) and measured almost eight feet long from nose to tail.[5]
Giant breeds


The following breeds are generally described as giant breeds:

Akbash Dog
Alaskan Malamute
Anatolian Shepherd
Armenian Gampr dog
Bernese Mountain Dog
Black Russian Terrier
Bloodhound
Boerboel
Brazilian Mastiff
Bucovina Shepherd Dog
Bullmastiff
Bully Kutta
Cane Corso[6]
Cão de Gado Transmontano
Caucasian Shepherd Dog
Central Asian Ovcharka
Dogue de Bordeaux
English Mastiff
Estrela Mountain Dog
Great Dane
Great Pyrenees
Greater Swiss Mountain Dog
Irish Wolfhound
Kangal Dog
Komondor
Kuvasz
Leonberger
Neapolitan Mastiff
Newfoundland[7]
Presa Canario
Pyrenean Mastiff
Rafeiro do Alentejo
Romanian Mioritic Shepherd Dog
Saint Bernard [8]
Scottish Deerhound
Spanish Mastiff
Šarplaninac
Tibetan Mastiff
Tosa Inu