Best Litter Box for Large Cats: How to Size It and 6 Picks

If your cat is a big one, you've probably seen the signs: back legs hanging over the edge, pee going over the side, or a cat that turns around three times and still doesn't fit. Most boxes labeled "large" are sized for an average cat. Here's how to tell what your cat actually needs, plus six boxes (manual and self-cleaning) that are genuinely roomy.

Quick picks

• Best overall: IRIS USA XX-Large High Sided ($39.99 list). 30 in long, 14 in walls, lower 6.5 in entry.
• Best stainless steel: Pematar XXL Stainless Steel. 26 × 18 in steel pan with a high-sided lid, for cats who pee high.
• Best self-cleaning for heavy cats: PetSafe ScoopFree OpenSky ($549.99). Open top and a 33 lb limit, the highest we found.
• Best self-cleaning globe for big cats: Litter-Robot 5 ($799). Rated for cats from 3 to 30 lb.
• Best proven self-cleaner: Litter-Robot 4 ($699). 3–25 lb cats, Wirecutter's top pick.
• Best wide entrance: Petlibro Luma ($599.99). Open globe with a 17.4 in entrance, for long cats up to 22 lb.

Step 1: Measure your cat, not the label

The AAFP/ISFM house-soiling guidelines give a simple rule: the box should be at least 1.5 times your cat's length, measured from the nose to the base of the tail.

Very few store-bought boxes are 30 in or longer. If your cat is longer than that, the same guidelines suggest a large under-bed storage container or a concrete mixing tray from a hardware store. Cut a low entry into one side if you need to. It won't win any design awards, but your cat won't care.

"Large" can mean heavy or long. A long, lanky cat mostly needs floor space. A heavy cat also needs a box rated for its weight, which matters a lot with self-cleaning machines (more on that below).

Step 2: Sides and entry height

Big cats often pee standing up or dig hard, so high sides help. But Cornell recommends low sides for older cats and cats with stiff joints, and plenty of big cats are seniors too. The best compromise is a box with high walls and a lower cut-out entry, like the IRIS (14 in walls, 6.5 in entry).

Covered boxes are usually a squeeze. Hood doors can be small. For example, Catit's Jumbo hooded box has a door opening of 10.4 × 9.6 in. Cornell also notes most cats prefer uncovered boxes. For a big cat, an open or high-sided box is usually the better bet.

Step 3: If you want self-cleaning, check the weight limit first

This is where big-cat owners get caught out. Every automatic box has a maximum cat weight, and many top out at 22 lb. Some are even marketed as good for large cats while still having that 22 lb limit. Here's how the models we track compare:

A weight limit isn't the only thing that matters. A long cat also needs room to turn around inside, so look at the entry size and interior too. For all 20 models we track, see the full self-cleaning comparison.

The picks

Manual boxes

This is the box we'd start with for almost any big cat. At 30 in long, it's one of the few store-bought boxes that meets the 1.5× rule for a cat up to about 20 in from nose to tail base. The 14 in walls catch high pee and enthusiastic digging, the 6.5 in curved entry keeps it easy to step into, and the open top gives your cat a clear view. It's also cheap. The catch is the footprint: 30 × 20 in won't fit every bathroom, so measure first. The Amazon link goes to the black version (model 588433).

If your big cat pees high or you're tired of plastic that holds smells, a stainless steel pan is worth a look. This one is 26 × 18 in, with a high-sided plastic lid that clips onto the steel pan for 12 in total height. By the 1.5× rule, 26 in suits a cat up to about 17 in long, so it's a bit shorter than the IRIS. Pematar is a smaller seller brand, and the specs here come from its Amazon listing, not a separate maker site. Check the listing photos to make sure the entry height works for your cat.

Self-cleaning boxes

The OpenSky has the highest cat weight rating we found (33 lb), and its open top means there's no hood for a big cat to squeeze under. PetSafe says the 8.5 L drawer holds up to two weeks of waste for one cat, and it works with most clumping litters. The app tracks weight and visits. The catch: we haven't found independent hands-on testing of the OpenSky yet, so this pick is based on specs. PetSafe offers a 45-day return window if it doesn't work out.

Whisker rates the Litter-Robot 5 for cats from 3 to 30 lb and up to 5 cats, the highest range among the enclosed globes we compared. Whisker's product description also says the extra headroom suits large breeds. It's the most expensive pick here, and Wirecutter hadn't tested the camera-free version when we checked. If your biggest cat is under 25 lb, the cheaper Litter-Robot 4 covers you. We link to Whisker directly for this one, and that link isn't a paid link.

For cats up to 25 lb, the Litter-Robot 4 is the safest self-cleaning choice. It's Wirecutter's top pick after hands-on testing, and it has the same 15.75 in square entry as the Litter-Robot 5. It uses regular clumping clay litter, and Whisker's 90-day trial lets you see whether your cat fits comfortably.

The Luma's 17.4 in entrance is the widest in our dataset, and it has no hood, which helps long cats that hate ducking. The limit is 22 lb, so it's a better fit for long, lean cats than very heavy ones. Wirecutter picked it for cats who prefer uncovered boxes, but warned that saving video costs a pricey subscription.

Big-cat litter box tips

• Fill it deeper. A bigger box with a thin layer still gets "missed." Keep enough litter for a good dig.
• Put a mat at the exit. Big paws carry more litter out.
• Scoop every day. A big box can look clean longer, but it still needs daily scooping.
• Still follow n+1. One box per cat plus one is the vet guideline, whatever the box size. See our guide to the best litter box for multiple cats.

FAQ

How big should a litter box be for a large cat?

At least 1.5 times your cat's length, nose to base of tail (AAFP/ISFM). For a cat that's 20 in long, that's a 30 in box, like the IRIS XX-Large.

What's the best self-cleaning litter box for a big cat?

Check the weight limit first. Of the models we track, the PetSafe ScoopFree OpenSky (33 lb) and Litter-Robot 5 (30 lb) have the highest limits. The Litter-Robot 4 goes to 25 lb. For more automatic picks, see our best automatic litter box guide.

Are covered litter boxes OK for big cats?

They can be, but hooded doors can be small, and Cornell notes most cats prefer uncovered boxes. For a big cat, a high-sided open box is usually easier.

My big cat pees over the edge. What helps?

Higher sides. The IRIS has 14 in walls, and the Pematar has a 12 in high lid. If the problem starts suddenly, check with your vet first. Cornell lists many medical causes of litter box problems.

Sources

Prices and specs were checked on Oct 19, 2026. Manufacturers change specs and prices; check the product page before you buy.

1. AAFP and ISFM Guidelines for Diagnosing and Solving House-Soiling Behavior in Cats (box size: 1.5× the cat's length; storage-container boxes)
2. Cornell Feline Health Center: Feline Behavior Problems: House Soiling (low sides for older cats, uncovered boxes)
3. IRIS USA: XX-Large Side Entry Cat Litter Box (30 × 20 × 14 in, 6.5 in entry, $39.99)
4. Amazon: IRIS USA XX-Large High Sided Cat Litter Box listing B0CVZRYCPW (black, model 588433)
5. Amazon: Pematar XXL Stainless Steel Litter Box listing B0F2H74Q26 (26 × 18 × 12 in, model MTCDH002-GREY)
6. PetSafe: ScoopFree OpenSky product page (open top, 8.5 L drawer, price)
7. Whisker: Litter-Robot 5 product page (3–30 lb, up to 5 cats)
8. PetSmart: Litter-Robot 5 listing (Whisker product description: headroom for large breeds, 22.2 × 27.25 × 29.9 in)
9. Whisker: Litter-Robot 4 product page (up to 4 cats, 3–25 lb)
10. Petlibro: Luma Smart Litter Box product page (17.4 in entrance, 2.2–22 lb)
11. PETKIT: Purobot Max 3 product page (3.3–22 lb)
12. Wirecutter: The Best Automatic Cat Litter Boxes (hands-on testing)
13. Litter Box Picks: master comparison dataset (every figure with its source URL)