How Many Litter Boxes, and Where to Put Them

Two cats, three boxes. That is the answer you will get everywhere, and it is roughly right.

What nobody tells you is that the rule's own authors are more careful than the internet is, and that the number of boxes matters considerably less than their size, which is where almost every box sold falls short.

The rule, quoted honestly

One litter box per cat, plus one spare.

The 2014 veterinary guidelines on house soiling, which are where this comes from, describe it as the historical rule of thumb and say plainly that it is not an absolute requirement.

That is a more useful sentence than the rule itself, because it tells you what to do when the rule and your house disagree. Three boxes in a one-bedroom flat with two cats who share everything happily is fine. Two boxes side by side in a corridor is worse than one box in a good place, for a reason we come to below.

The finding nobody selling boxes wants to publish

Here is the one that matters, and it is a measurement.

The guidelines say a litter box should be about one and a half times the cat's body length. Work that through for an average cat and you land at a box roughly 22 to 32 inches long (around 56 to 81 cm).

Now the shop shelf:

Even the jumbo is at the bottom of the recommended range. The standard is not close.

And there is direct evidence behind it: a 2014 study found cats significantly preferred a box measuring 86 x 39 cm, about 34 x 15 inches, over a smaller one. That is larger than anything most shops stock as a litter box at all, which is why a plastic storage tub with a side cut down is such a common recommendation from people who have read the research.

⚠️ One honest wrinkle: two authoritative guidelines, from 2014 and 2021, define "one and a half times the cat's length" differently. One measures nose to base of tail, the other nose to tip of tail. Nobody has reconciled them, so treat the range as a range.

Placement, and the rule that explains the corridor problem

Placement matters as much as the count, and there is one rule here that we have not seen on any competing page:

Two boxes side by side are one box, as far as a cat is concerned. And openings should not face each other.

Which explains the failure mode people run into constantly: three trays lined up neatly in the utility room is, functionally, one location. If the point of the spare box is that a cat can always reach one without passing another cat, then lining them up defeats the entire purpose.

So:

• Spread them out. Different rooms, and one per floor in a house with stairs.
• Away from food and water.
• Away from noisy appliances, especially ones that start on their own. A boiler firing while a cat is mid-squat teaches a lesson you will spend months undoing.
• Never in a dead end. A cat needs to see what is coming and have a way out that is not past it.

Which litter, and does a lid matter?

Litter type has a clear answer, and decades of preference studies converge on the same one: unscented, fine-grained, clumping clay. That is not the most expensive option and it is not the one with the nicest packaging.

Covered or uncovered has no clear answer, and the honest version is the interesting one. A 2013 study found no population-level preference: cats as a group did not favour covered or uncovered. What it did find was real individual variation, meaning your cat has an opinion even though cats in general do not.

The practical translation: offer both if you are unsure, and let the cat vote.

Skip scented litters and deodorising powders. You are solving your problem with the cat's nose.

Cleaning, and a reason you have not heard

Scoop daily, change fully on the schedule your litter type needs.

The reason everyone gives is smell. There is a better one, and it is public health: Toxoplasma oocysts shed in cat feces are not immediately infectious. They need a period in the tray to become so. Scooping daily takes the litter box out of that window entirely.

That single fact is worth more than every deodorising product on the shelf, and none of the competing pages we checked mention it.

⚠️ What to clean it with matters. Disinfectants containing chloroxylenol, the active ingredient in some common household products, are toxic to cats. Hot water and a mild detergent, rinsed properly, is the safe answer.

The litter box is a diagnostic instrument

This is the part of the page that could save an animal, so it goes in bold.

What comes out of the box, and how often, is often the first sign of urinary disease, kidney disease and diabetes. Changes worth acting on:

• More urine, or more visits
• Less urine, or straining
• Blood
• Suddenly going outside the box, in a cat that never did

⚠️ A male cat straining in the box and producing nothing is a life-threatening emergency. A complete urethral blockage can kill within 24 to 48 hours, on Cornell's own figure. It is not a wait-and-see, it is not a morning-appointment, it is now.

Anything that worries you about your cat is a reason to call your vet, and out of hours, an emergency clinic. Nothing on this page is ever a reason to wait.

If your cat has started going outside the box, that is a separate subject with its own causes, and the first question is always a medical one, because a cat that strains without producing urine is an emergency. Why a cat pees outside the litter box works through the causes in the order a vet does. The standing-up version, small amounts sprayed on vertical surfaces, is marking, and our spraying guide covers its triggers.

Words, by market

Litter box in the United States and Canada. Litter tray in the United Kingdom. Both are used in Australia. Litter itself is litter everywhere.

What to take away

• One per cat plus one is a rule of thumb, and the guidelines that gave us it say so themselves.
• Size beats count. The guidance implies 22 to 32 inches long, and even a jumbo box is at the bottom of that.
• Two boxes side by side are one box to a cat. Spread them out, one per floor.
• Unscented, fine, clumping clay wins the preference studies. Scent is for you, not the cat.
• Covered versus uncovered has no population answer and a real individual one. Let the cat vote.
• Scoop daily, and the reason is Toxoplasma rather than smell.
• A male cat straining and producing nothing is an emergency, and the window is 24 to 48 hours.

More on what a cat will actually use, and where to put it, in what makes a scratching post work.