The n+1 rule
The golden rule of litter boxes is beautifully simple: one box per cat, plus one extra. Two cats need three boxes; three cats need four. Cats are territorial about their bathrooms, and a clean, available box is the single biggest factor in avoiding accidents outside the box. The extra box is your buffer for busy days, late scoopings, and the occasional feline disagreement about whose turn it is.
One per floor, minimum
Cats do not like climbing stairs when nature calls urgently — kittens, seniors, and any cat in a hurry will simply find a closer spot (your rug). Every level of your home needs at least one box, even if the n+1 math would allow fewer. A two-story home with one cat still wants two boxes: one up, one down.
Size matters more than style
A box should be about 1.5 times your cat's body length so they can turn and dig comfortably. Big cats (15 lb and up) need jumbo boxes — a large cat squeezed into a standard box will hang over the edge, and the mess ends up on your floor. As for covered versus uncovered: most cats strongly prefer uncovered boxes. Covers trap odors inside (great for humans, miserable for the cat) and make some cats feel ambushed. High-sided or top-entry boxes are a good compromise for enthusiastic diggers.
Location, location, location
Put boxes in quiet, low-traffic spots with an escape route — never wedged in a corner where the cat feels trapped, and never right next to food and water (cats do not dine where they toilet). Laundry rooms and spare bathrooms work well. Avoid noisy appliances: a box beside a rumbling dryer will go unused. Scoop daily and do a full litter change regularly, and your n+1 setup will quietly do its job for years.
