My husband and I live in a one-bedroom, 800-square-foot apartment in New York City. We have two cats, and though I fantasize about filling my pockets with kittens and making a break for it every time I pass an adoption fair, we probably won’t bring a third cat into the household. Do I worry about multiplying litter boxes? Or complicating my guys’ pair bond? Or what a newcomer would add to the diameter of cat-hair tumbleweeds in our space?

The truth is simpler (and perhaps creepier) than that: I maintain a strict 1:1 cat-to-lap ratio because I don’t want our pets to feel neglected. It’s a rule that makes little sense — our cats are just as likely to pile together on top of me or my husband as they are to seek attention from us separately — but it’s a rule I’ve continued to follow.

There’s no science in that, of course, and I can’t guarantee that I’ll never be seized by the need to bring another cat home. So how do you know how many cats your household can handle? I considered what the Internet had to say — which, as with most subjects, was in turns helpful, entertaining, and kind of frightening — and then got professional advice from Dr. Jeannine Berger (a vet and behavior specialist at the San Francisco SPCA) and Pam Johnson-Bennett (an author and cat expert). Here’s where we ended up.

Rule No. 1: There is no “rule”

Some people swear up and down that you should never have more cats than bedrooms; others argue that all will be well if you have more litter boxes than kitties, or if you have at least 200 square feet of space per cat. Magical formulas are attractive, but they aren’t very useful.

“Determining how many cats you have should be based on your ability to provide [for] the emotional, physical, nutritional, and medical needs of each cat, and whether each cat has quality space, safe retreats, [and the ability to] move about without feeling threatened,” Johnson-Bennett says. “I’ve done consultations in 3,000-square-foot homes where two cats couldn’t coexist peacefully.”

I’ve seen situations like that, too; friends of mine in Chicago have divided their home with a baby gate for years because of their two cats’ extremely irreconcilable differences.

Berger concurs: “So much depends on the individual cats — their age, energy level, history together, and so on.”

“N+1” is a pretty good litter box guideline

“We generally recommend that you have one more [litter box] than the total number of cats,” Berger told me (and Johnson-Bennett agrees). “This is especially important if there are cats in the house that don’t get along, or are shy, or have any kind of medical problems.”

Sometimes cats will “cope” with sharing litter boxes, she said, but that doesn’t mean they prefer it that way. That was hard for me to hear, because we’ve always had just one box for our two cats (whoops).

“I know in small apartments that can be challenging,” Johnson-Bennett says, “but even having boxes that are a few feet apart can ease multi-cat tension.”

Box size is also important, she says. Some people who live in small apartments buy litter boxes to match the size of the living space that are too small for the size of the cat. She says no matter how small the apartment, litter boxes must be matched to the size of the cat.

Berger explains that keeping them clean is crucial: “What matters most is that the litter box(es) are kept clean — even cleaning after each elimination if it’s a shared box — because the most common reason for inappropriate urination issues in indoor cats is because the box is too dirty for their liking.”

That we can certainly do.

Vertical space is crucial

Many people argue that a home’s footprint is less important than the ways in which a cat or cats can maneuver in it — specifically, the ways in which they can go up.

“What matters most to a cat is the quality of the space,” Johnson-Bennett says. “Cats live in a vertical world, and we live in a horizontal world. In a small space, think up by using cat shelves, walkways, cat trees, and window perches. You’d be surprised how much space you can make use of even in the tiniest of living quarters.”

For inspiration, Berger recommends looking at The Cats’ House, Bob Walker’s feline paradise in San Diego. It has remarkable amounts of vertical territory for cats.

Three words: Windows, windows, windows

If you’re hunting for a home that’ll satisfy you and your furry pals, one architectural feature is especially high-value. My two experts described windows in almost exactly the same way: They operate as “cat TV,” and they’re enormously important in offering your cats quality space.

“If you put a cat tree or a window perch in front of the window,” Johnson-Bennett says, “it increases the value: Now your cat has a place of his own to nap in the sun.”

When you’re dealing with more than one feline, that cat tree should have a lot of branches.

“In a multi-cat environment,” she says, “even if that environment is very small, the use of a multi-perched cat tree can encourage cats to share a space without disrupting any status issues between them.”

Pudgy cats aren’t cramped, they’re overfed or bored

Some people on message boards (sorry, Internet, but I’m calling you out on this one) argue that you know your cats don’t have enough room if they gain weight. To put it bluntly, those people are wrong.

“Weight gain — unless there’s a medical reason for it — is due to calorie input vs. energy input,” Johnson-Bennett says.

Cats can’t feed themselves, and it’s our responsibility as their caretakers to give them an appropriate amount of food — and to make sure there’s plenty for them to do.

“You can provide exercise for your cat, even in a small space; your cat doesn’t need to run 20 miles a day to stay in shape,” Johnson-Bennett says.

She advises considering the way cats hunt in the wild — it’s all about stalking and pouncing. You can conduct interactive play sessions in a small space, and your cat can get beneficial exercise in a way that provides fun and satisfaction.

“Just as cats need quality space, they need quality time — yours,” she says.

How many cats do you have? Do you have a formula for how many your living space will accommodate? Tell us in the comments.

Read more by Lauren Oster.

About the author: Lauren Oster is a freelance writer and editor in New York City. She and her husband share an apartment on the Lower East Side with Steve and Matty, two Siamese-ish cats. She doesn’t leave home without a book or two, a handful of plastic animals, Icelandic licorice mints, and her camera. Follow her on Twitter or Instagram.