There are many things to consider when owning more than two cats. After reading this I assure you, you will never end up being the crazy cat lady of your neighborhood. Going beyond a pair you have to really take your living space, litter boxes, accessible windows, and outdoor space into consideration. Here are three ways to help you decide how many cats is just too many.
One Cat per Bedroom
This is a basic rule that will never get you in trouble with over occupying your space. If you have a one bedroom home, one cat is plenty but you can go up to two without being overcrowded. For a two bedroom, it is two cats, for three bedrooms, three cats, I am sure you get the idea here.
Single, Double, And Two-Story Living
With the addition of floors, you can add more cats. A single floor living space needs to follow the above ruling exactly. A ranch which is two floors (basement and first floor) can add in an extra cat beyond the bedroom number so long as the basement space is clean and livable. A two-story home generally has 2 floors and a basement space. Again, you can add an extra cat for the upstairs and another if the basement is clean and livable.
This is a very basic guideline with a square footage of a space. Anything under 1000 should not have more than 2 cats. For every 500 square feet after 1000, you can add one cat. So a home that is 1500 square feet, you can usually house 3 cats comfortably. A home that is 2000 can be fitting for 4 cats.
Things to also consider :
Dogs: If your home also occupies dogs, for every dog you have to minus 1 or 2 cats to the rules above.
Children: If you have children sharing one bedroom, minus 1 cat for this as well.
Litter Boxes: One box is enough for 2 cats, BUT you will want an extra litter box for every cat after that. So owning 4 cats, you will want a minimum of 3 boxes.
Below is a basic chart to show you how many cats per bedroom, per livable floor space you can have under one roof as a basic guideline. Outside of this, individual cat personalities will greatly play a role in how many cats can be in one home. Some cats are more forgiving of space, whilst others are more territorial.
NOTE: Outdoor enclosures will allow for more cats under one home as it doubles as a livable/play area for your cat. Depending on the size, you can have as many as 3 more cats under one roof.