What Size Dog Crate you'll need depends not only on the size of your dog, but also on the purpose of the crate. Here's everything you need to know about What Size Dog Crate to buy.
How Big is Your Dog?
Obviously, the same size crate isn't going to work for a Poodle and a German Shepherd. Consider not only the dog's weight, but also his width, length, and height. Make sure he will fit comfortably through the opening and be able to turn around and move a little once inside.
Activity Level and Personality of the Dog
Consider your dog's temperament and activity level when choosing a crate. Is he content to sit relatively still for long periods of time or does he like to pace and stretch throughout the day? A roaming dog may rebel from being too restricted in a small, confined space.
Does the dog have a social personality? Does he have separation anxiety? These are traits to consider when deciding What Size Dog Crate to buy. If the dog is likely to bark all day in the confined space without attention, you may need to come up with an alternate solution.
What is the Purpose of the Crate?
If the crate is strictly for potty training, it either needs to be just slightly bigger than your dog (with some room for growth if he is a puppy). 
Too much space will allow the dog to go in one corner of the crate, but still have enough room to sit comfortably elsewhere within the cage. The dog should not be allowed to go potty in his crate. Even though it is one of their basic instincts to not soil their living area, mistakes will sometimes occur. You may want to try using puppy litter or training pads when first crate training your puppy.
Will You Be Using the Crate for Traveling?
More people are taking their pets with them when they travel now. If you intend on using the crate to confine your pet for traveling, you'll need to buy a rather small crate to fit in the car, camper, or airplane. If the cage is too large for the dog, he will likely go potty in the crate, especially when he is in unfamiliar territory.
