When selecting a crate size it is extremely important that it be the proper size. It is not a difficult task to determine the proper size of your dogs new home. You should always select the size that your dog will require as an adult, your local pet shop can assist you in making this selection.
Your puppy should be crated each and every time you leave him by himself in the home. This is for his safety as well as for your mental well being. All puppies are chewers and they do not typically exercise good judgment in deciding what they should or should not chew on.
Puppy's can't tell the difference between a proper chew toy and the lamp cords or telephone wires. Chewing into an electrical wire can be fatal for your dog as well as start a fire in the home.
If the dog stays n his crate while your away, you prevent him from harming himself and maybe burning down the house.
An uncrated puppy can find all kinds of mischief to get into in an uncharted house.
If your new puppy chews on the leg of your dining room table while you're gone, you will probably get angry with him when you return. Your dog will than make the association that your returning home means he will get punished. (He will not recall carving up your furniture and will not associate your anger with that)
The crate will also provide privacy and a barrier between your puppy and other distractions. For example, you can feed your puppy in his crate if you have small children, thus allowing him to eat in peace and unbothered.
A crate will provide a place of safety and comfort to your puppy and is a valuable part of his training.