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Litter Boxes and Litter: What Cats Prefer

Updated July 30, 2026

A tabby cat peers out from inside a covered, hooded litter box on a wood floor.
Tom Thai / Wikimedia Commons

By Morgan Reyes

That "Cats Hate Covered Boxes" Rule Doesn't Really Hold

That "cats hate covered litter boxes" line you've seen repeated everywhere doesn't hold up, and neither does the opposite claim. A controlled study found most cats simply don't care, and a second study suggests the covered-box preference some sources report may really be about box size, not the cover itself.

QuestionFinding
How many boxes?Number of cats, plus one
How big?Bigger than most commercial boxes; size may matter more than cover
Covered or uncovered?No overall preference in a controlled 28-cat study; likely confounded with size in other research
Litter type?Fine-grained clumping clay, most consistently preferred

How many boxes, and how big

The standard rule: one litter box per cat, plus one. A single-cat household needs two boxes, not one, and the "plus one" isn't padding, it's there specifically to avoid forcing a cat to use an already-soiled box when another cat (or the same cat, recently) has used the only other one.

Size matters, and most commercial "cat-sized" boxes undersize relative to what cats prefer. Bigger boxes give a cat more room to turn, dig, and position themselves comfortably, and the size question turns out to matter more than the covered-versus-uncovered question below, which is the genuinely underused finding here.

Covered vs uncovered: what the research found

A controlled study is the right place to start, because it isolated the variable properly. Twenty-eight cats were given a choice between an identically-sized covered and uncovered box (both built from the same 82.5 × 50.2 × 47.3 cm plastic tub, so size wasn't a confound). The result: no significant overall preference between the two styles. Broken down individually, 70% of cats showed no preference at all, 15% significantly preferred the covered box, and 15% significantly preferred the uncovered one.

Diagram comparing an uncovered litter box and a covered litter box of the same footprint size, one open-top and one with a hood and entry cutout.
Illustration of the covered-vs-uncovered comparison a controlled study tested. Both boxes share the same footprint -- when size is held equal, most cats showed no real preference for the cover.
  1. 1Uncovered box: open top, no lid
  2. 2Covered box: same 82.5 x 50.2 cm footprint, with a hood and entry cutout
  3. 3Size bracket: both boxes share the same footprint -- the variable the underlying study held constant

Here's where it gets genuinely interesting, and where most consumer advice oversimplifies. A separate two-part study design specifically tested whether box size, not the cover itself, might be driving the "cats prefer covered boxes" claim some sources repeat. In the first part, with 13 cats and boxes of equal surface area, there was only a weak lean toward the covered box, not reaching standard significance. In the second part, with 12 different cats, the covered box's surface area was made 17% larger than the uncovered one, and the preference for the covered box became statistically significant.

Put plainly: when covered and uncovered boxes are the same size, cats mostly don't show a real preference either way, per the controlled 28-cat study. The "covered boxes win" claim some sources repeat may really be measuring "bigger boxes win," dressed up as a cover preference.

Beyond the preference question, covered boxes carry practical downsides worth knowing regardless of what a cat prefers: they concentrate odor more than an open box, and they make it harder for an owner to notice early signs of a health problem (straining, blood, unusual frequency) since the box itself blocks the view. That's not a small thing to give up. Watching what's happening in the box is one of the easiest early-warning signs an owner has, and it's worth protecting on purpose rather than trading away for a tidier-looking room.

Litter type

Fine-grained clumping clay litter is the substrate most consistently associated with cat preference across the research consulted. If you're troubleshooting a cat that's avoiding the box entirely, litter type and cleanliness are worth checking before assuming the box style itself is the problem.

Worth saying plainly

The advice to avoid covered litter boxes usually gets stated as settled fact, and a controlled study says most cats genuinely don't care either way. What may be driving the "cats prefer covered boxes" claim in some other research is box size, not the cover, since the preference only showed up once the covered box was also bigger. Get the size and count right first. The cover is a secondary decision, and the odor/visibility tradeoffs of a covered box are worth weighing on their own terms.

Bottom line: the standard box-count rule (cats plus one) and adequate size matter more than the covered-versus-uncovered debate. A controlled 28-cat study found no significant overall preference between covered and uncovered boxes of the same size; a separate study suggests the "cats prefer covered" claim circulating elsewhere may really be a surface-area confound, since the preference only appeared when the covered box was also larger. Fine-grained clumping clay is the most consistently preferred litter type. If your cat is avoiding the box, check size, cleanliness, and litter type before assuming the cover itself is the issue.

FAQ

Do cats prefer covered or uncovered litter boxes?

No significant overall preference in a controlled, size-matched study. A separate study suggests the "covered is preferred" claim elsewhere may really be about box size. See the full breakdown above.

How many litter boxes do I need for one cat?

Two: one per cat, plus one extra.

What litter box size and type do cats prefer most?

Larger than most commercial boxes offer, with fine-grained clumping clay as the most consistently preferred litter type.

Keep reading

A Note on Scope

This guide covers litter box and litter preference research. It is not veterinary advice. A cat suddenly avoiding the litter box, especially with straining or signs of pain, needs a vet visit, not a box upgrade.

Sources