There is a saying that we should choose a cage three times the size of a dog, but how can we calculate it to be three times the size? The top and corner of the cage are virtually unusable space for dogs if measured in volume. Others say it's just enough width for the dog to turn around. Personally, I think it's simpler to choose the size of the cage, which is twice the length of the dog. It should be suitable for the dog. But if the dog you buy is a puppy, consider its growth, so the cage must be purchased according to the adult size of the dog.