1.   Measure your pet from the top of the shoulders to the chest, just behind the front legs. Then measure the width of your pet at the widest point.  This will be either the shoulder or hip area.

2.  Determine your pet's weight.

3.  Select the correct door size based on your pet's measurements and weight. You will need a pet door with an opening size that is bigger than your pet's measurement.

Cat doors come in all types and sizes.

They can be installed in a wall, a door, sliding glass doors, metal doors, aluminum panels, and just about anywhere you want. PetSafe shows how to measure your cat to obtain the right size cat door and how to choose the kitty door best for you.

One of the biggest questions people face is where to install their new cat door. We believe the ideal place is in a wall. Depending on your living quarters, we would place the cat door in a room or area that can receive some tracking-in-dirt that is inevitable when using cat doors. Rooms, kitchens, second bedrooms, dens, and other areas other than the main living area is usually a good idea.

Placing a floor mat on the inside of the cat door is also recommended. A great advantage of having the cat door installed in a wall (instead of a door) is that no one needs to know that you have a cat door.

If you are renting your place of residence, or do not want to cut permanent holes in a wall or door, you can still have a cat door. In this case, you will want to install the cat door in either a sliding glass door, or a regular door. Cat doors that are made for sliding glass doors actually come as a whole panel (patio cat door) that you install in the doorway section, therefore it does not permanently affect your sliding glass doors in any way.

If you do not have sliding glass door for a patio cat door, you still have another option. Purchase an inexpensive door at your local home-improvement store, or door store. Replace the permanent door with your new inexpensive door by removing the door via its hinges. Now you can install the cat door in the new door, and when you move, simply put the permanent door back in its place!

As you can see, just about anyone can have a cat door! Once you get one, you won't know how you ever lived without it.