A large litter box for a big cat is mostly a question of length. The 2014 AAFP and ISFM guidelines set the minimum at 1.5 times the cat, measured nose to tail base, so a 20 in (51 cm) cat needs 30 in (76 cm). Two boxes below reach that on their outside size. For a longer cat, a concrete mixing tray from a hardware store goes further.
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Which large litter box to choose
For most big cats up to 20 in (51 cm) long, our pick is the IRIS XL Open-Top with Shield: the longest published outside length here, with an open top and a low entry.
Will it fit? IRIS USA XL Open-Top with Shield
- Footprint
- 30.2 x 20 in (77 x 51 cm), 4.2 sq ft (0.39 m²)
- Height
- 13.1 in (33 cm)
- Covers a cat up to
- 20 in (51 cm) on the outside length
- Best for
- One big cat and a wall at least 31 in (79 cm) long
- Skip if
- Your cat is stiff and needs a step you know is low
Details
Product prices and availability are accurate as of the date/time indicated and are subject to change. Any price and availability information displayed on Amazon.com at the time of purchase will apply to the purchase of this product.Go by your cat’s length first, then your floor:
- Up to 14 in (36 cm), tight bathroomVan Ness High Sides Giant.$28.53 Price as of Nov 2, 2026, 03:52 UTCCheck price at Amazon
Details
Product prices and availability are accurate as of the date/time indicated and are subject to change. Any price and availability information displayed on Amazon.com at the time of purchase will apply to the purchase of this product. - 15 to 17 in (38 to 43 cm)The Petmate Giant once it is back in stock, about 1 sq ft (0.09 m²) smaller than the 30 in (76 cm) pair; until then, the KittyGoHere Jumbo.$75.00 Price as of Nov 2, 2026, 03:53 UTCCheck price at Amazon
Details
Product prices and availability are accurate as of the date/time indicated and are subject to change. Any price and availability information displayed on Amazon.com at the time of purchase will apply to the purchase of this product. - Older or stiff and up to 18 in (46 cm)KittyGoHere Jumbo, for the 3 in (7.6 cm) step.$75.00 Price as of Nov 2, 2026, 03:53 UTCCheck price at Amazon
Details
Product prices and availability are accurate as of the date/time indicated and are subject to change. Any price and availability information displayed on Amazon.com at the time of purchase will apply to the purchase of this product. - 18 to 20 in (46 to 51 cm)The IRIS XL Open-Top with Shield, or the IRIS Side Entry if your cat stands to pee.
- Over 20 in (51 cm), or working to the AAHA tail-tip ruleA concrete mixing tray or an under-bed storage container (the longer options).
Key takeaways
- Measure first: nose to tail base, times 1.5, is the shortest box the AAFP and ISFM accept. → how to measure
- Makers print outside sizes only, so the floor your cat stands on is smaller. → the five boxes side by side
- An open top lets you see waste at a glance, and the AAFP and ISFM prefer it for most cats. → covered or open
- Cat longer than 20 in (51 cm)? None of the five boxes here is long enough; a concrete mixing tray or under-bed container is. → longer options
Large litter boxes compared by length
Not sure how long your box needs to be? The cat measuring tool works it out from one measurement.
| Box | Outside length | Covers a cat up to (1.5 times rule) | Footprint and floor | Height | Entry |
|---|---|---|---|---|---|
| IRIS USA XL Open-Top with Shield (588433) | 30.2 in (77 cm) | 20 in (51 cm) | 30.2 x 20 in (77 x 51 cm), 4.2 sq ft (0.39 m²) | 13.1 in (33 cm) | Low; height not given |
| IRIS USA XX-Large Side Entry (500493) | 30 in (76 cm) | 20 in (51 cm) | 30 x 20 in (76 x 51 cm), 4.2 sq ft (0.39 m²) | 14 in (36 cm) | 6.5 in (17 cm), side |
| KittyGoHere Senior Cat Litter Box, Jumbo | 28 in (71 cm), listing | 18 in (46 cm) | 28 x 22 in (71 x 56 cm), 4.3 sq ft (0.40 m²) | 9 in (23 cm) | 3 in (8 cm), gate to 5 in (13 cm) |
| Petmate Giant Litter Box (22211), unavailable at Amazon on Oct 16, 2026 | 25.56 in (65 cm) | 17 in (43 cm) | 25.56 x 18.3 in (65 x 46 cm), 3.2 sq ft (0.30 m²) | 10 in (25 cm) | Sloped; height not given |
| Van Ness High Sides Giant (CP3HS) | 21.25 in (54 cm) | 14 in (36 cm) | 21.25 x 17.63 in (54 x 45 cm), 2.6 sq ft (0.24 m²) | 9.25 in (23 cm) | Not given |
Every maker here gives overall dimensions and no inside floor size. The usable floor is shorter, by an amount none of them publishes, so read the cat column as a ceiling. If your cat measures more than 20 in (51 cm), skip ahead to the storage box and mixing tray options.
How long a litter box for big cats has to be
Run a tape from the tip of your cat’s nose to where the tail meets the body and multiply by 1.5. The AAFP and ISFM house-soiling guidelines treat the result as the shortest acceptable box, and so do this page and the measuring tool. AAHA and AAFP’s 2021 life stage guidelines run it on to the tip of the tail, which lengthens the box. Pick one version and do not mix them.
The evidence favors long boxes as well: the AAFP and ISFM cite a study in which adult cats chose a box 34 in long and 15 in wide (86 x 39 cm) over a smaller one, at least 3.8 in (9.7 cm) longer than any of the five boxes below. Labels will not help you: every box sold simply as Large in the Amazon listings we pulled on Oct 16, 2026 was shorter than the Petmate Giant below. Self-cleaning globes are no exception: the Litter-Robot 3 vs 4 comparison checks Whisker’s inside floor against the same 1.5 times rule.
Giant is no standard either. Van Ness uses the word for 21.25 in (54 cm) and Petmate for 25.56 in (65 cm). Our litter box sizes and styles page sets out the evidence on every style.
IRIS USA XL Open-Top with Shield: top pick for cats up to 20 in (51 cm)
IRIS sells this box on its own site as the XL Open-Top Cat Litter Box and on Amazon as the XX-Large High Sided Cat Litter Box, both under model 588433. The maker gives 30.2 x 20 x 13.1 in (77 x 51 x 33 cm), the longest published figure here.
It is our pick because it pairs that length with an open top, which the AAFP and ISFM prefer because waste is easy to see, and a low entry that IRIS pitches at kittens and older cats. IRIS also claims twice the area of its standard pan and says the side and back walls keep litter from scattering. It does not say how low the entry is, so a stiff cat should start with the KittyGoHere.
IRIS USA XX-Large Side Entry: the tallest walls
The XX-Large Side Entry, model 500493, has nearly the same footprint, 30 x 20 in (76 x 51 cm), with 14 in (36 cm) walls and, by IRIS’s figures, a 6.5 in (17 cm) curved entrance. The AAFP and ISFM note that high sides catch urine from cats that stand to pee, and IRIS markets this box for Maine Coons, Ragdolls and Savannahs. Skip it for a cat with sore hips, because that step is more than twice the KittyGoHere’s.
KittyGoHere Jumbo: a 3 in (7.6 cm) step for an older big cat
NE14 Pets sells the KittyGoHere line. Its Jumbo pan has a front opening 3 in (8 cm) high, and a removable gate raises it to 5 in (13 cm). The maker’s page gives no dimensions, so the size comes from the Amazon listing: 28 x 22 x 9 in (71 x 56 x 23 cm), length for a cat up to 18 in (46 cm).
That low front is what the veterinary sources ask for. Cornell says elderly cats and cats with mobility problems need low sides, and the AAHA and AAFP guidelines want edges a senior cat can get over easily. The trade is a 9 in (23 cm) wall, less of a barrier for a cat that sprays high.
Will it fit? KittyGoHere Senior Cat Litter Box, Jumbo
- Footprint
- 28 x 22 in (71 x 56 cm), 4.3 sq ft (0.40 m²), per the listing
- Entry
- 3 in (8 cm); 5 in (13 cm) once the gate is in
- Covers a cat up to
- 18 in (46 cm), nose to tail base
- Best for
- An older or arthritic big cat
- Skip if
- Your cat stands to pee, or you want the maker’s own size figures
Details
Product prices and availability are accurate as of the date/time indicated and are subject to change. Any price and availability information displayed on Amazon.com at the time of purchase will apply to the purchase of this product.See the vet before buying a new box. A big cat that starts going on the floor beside its box, or an older one that hesitates at the edge, needs a checkup first. Cornell’s list of causes includes urinary disease, kidney and thyroid problems, diabetes and age-related trouble getting around. A male cat that strains and passes little or no urine needs a vet right away.
Petmate Giant: 25.56 in (65 cm) on a smaller floor
Petmate lists the Giant Litter Box (model 22211) at 25.56 x 18.3 x 10.02 in (65 x 46 x 25 cm). It covers a cat up to 17 in (43 cm) and, at 3.2 sq ft (0.30 m²), needs about 1 sq ft (0.09 m²) less floor than either IRIS box. Beside a toilet, that square foot can decide whether a box fits at all. Amazon showed it as unavailable on Oct 16, 2026, so it has no link here until it returns; the KittyGoHere Jumbo is the in-stock box nearest its size.
The maker describes a sloped entry for older cats and kittens, high sides against scatter and room for over 30 lb (14 kg) of litter, and says the pan is made in the USA from 95% pre-consumer recycled plastic.
Van Ness High Sides Giant: compact, for cats up to 14 in (36 cm)
At 21.25 x 17.63 x 9.25 in (54 x 45 x 23 cm) and 2.6 sq ft (0.24 m²), model CP3HS is the shortest and smallest box here. Buy the Van Ness High Sides Giant for a cat that looks big but measures 14 in (36 cm) or less, whatever the name suggests. Van Ness says the extra-high sides contain digging and spraying and that the plastic is BPA-free. Its care notes recommend liners, which the AAFP and ISFM say to avoid; many cats dislike how a liner feels.
Extra large litter box options longer than 30 in (76 cm)
When the pet aisle runs short, the AAFP and ISFM point to hardware and department stores:
- A concrete mixing tray. Their example is smooth, heavy plastic, 36 in long, 24 in wide and 8 in deep (91 x 61 x 20 cm): enough for a 24 in (61 cm) cat, on 6 sq ft (0.56 m²).
- An under-bed storage container, long and low.
- A sweater box, the lidded tub sold for folded clothes.
The guidelines picture a storage container with one side cut down for easy entry, which they say helps an older cat. Measure the floor of a tub rather than the label, since tubs often narrow toward the base, and if you cut an entry, sand the edge until no sharp plastic is left.
Keep the lid. The AAFP and ISFM suggest standing it upright behind the box to protect the wall, a free fix in a rental.
Covered or open: what a hood costs a big cat
Length, mostly. IRIS lists its Hooded Cat Litter Box, Jumbo at 21 x 18.75 x 17 in (53 x 48 x 43 cm) outside but 15.25 x 14 in (39 x 36 cm) inside, enough for a 10 in (25 cm) cat. In the one controlled study, by Grigg and colleagues, 28 cats showed no overall preference between covered and open, and the eight that did have a favorite split evenly. Those boxes, though, were storage bins about 32.5 in (83 cm) long, scooped daily. The AAFP and ISFM still recommend open boxes, and they warn that a small covered box can make it hard for a larger cat to posture normally.
If your cat insists on a hood, check the inside floor against your number. Cornell notes that a cover holds odor in with the cat, which the litter box smell guide deals with.
Where a 30 in (76 cm) litter box fits in a small apartment
A 30 x 20 in (76 x 51 cm) box needs a clear 30 in (76 cm) along one wall plus room at the entry for a big cat to turn, and none of the guidelines we read puts a number on that space. In a studio the usual spots are the bathroom floor beside the tub, a closet with the door hooked open, or the end of the sofa. The placement guide for small apartments weighs each one, and the space-fit planner draws any box on your floor to scale.
A bigger box does not cancel the second one. AAHA and AAFP guidance counts cats plus one, each box in a separate spot, and a pair set next to each other counts only once. For a pair of cats, the guide to litter boxes for two cats covers fitting three into a small home.
Plan for more litter, too. At 2 in (5.1 cm) deep, the top of Cornell’s 1 to 2 in (2.5 to 5.1 cm) range, a 30 x 20 in (76 x 51 cm) footprint holds up to about 20 liters, against about 12 for the Van Ness, and in a walk-up you carry all of it up the stairs. Scoop at least once a day whatever the size (AAFP and ISFM).
Boxes we left out, and why
Stainless steel boxes turn up all over Amazon’s results for this search, none listed as long as the IRIS pair in the results we pulled, and their sellers claim steel never holds odor. None made the cut. We found no maker product page for any of them: the brand sites that turned up only link to Amazon, one with its own affiliate tag, and we list a box only when its maker publishes specs we can check. A jumbo plastic pan went for the same reason. Litter, depth and cleaning are on the litter hub.
Questions about large litter boxes
What size litter box does a big cat need?
One and a half times the cat’s body, nose to tail base, at the very least, under the 2014 AAFP and ISFM guidelines. That works out to 25.5 in (65 cm) for a 17 in (43 cm) cat and 30 in (76 cm) for a 20 in (51 cm) cat. Measure to the tail tip, as AAHA and AAFP do, and the answer grows.
What is the biggest XL or jumbo litter box?
In this guide, the IRIS XL Open-Top at 30.2 in (77 cm) outside, with the IRIS Side Entry a fifth of an inch behind. Names mislead: a hooded box sold as Jumbo has 15.25 in (39 cm) of inside floor. Beyond 30 in (76 cm), a concrete mixing tray or a long storage tub takes over from pet store boxes.
Is one extra large litter box enough for two cats?
Not under the usual count. AAHA and AAFP guidance gives two cats three boxes in three places, and a long box is still one box, however much floor it covers. Use it as one of the three, sized for the longer cat of the pair, and plan the other two spots around it.
How do I switch a cat to a bigger litter box in a small apartment?
Add the new box before taking the old one away: in its own spot if the floor allows, beside it if not, with the same litter at the same depth. Once the cat uses the new box daily, retire the old one, or keep it as the spare if it passes the AAFP and ISFM 1.5 times rule.
Do large cats need a high sided litter box?
Only some do. Height helps a cat that pees standing up, which the AAFP and ISFM flag, or one that digs hard. A stiff or elderly cat needs a low way in instead, and tall sides with a low front, as on the IRIS boxes or a cut-down tub, serve both kinds of cat.
What works as a litter box for a very large cat?
Hardware and storage aisles stock what pet stores lack. The house-soiling guidelines name a concrete mixing tray, an under-bed storage container and a sweater box. Choose smooth plastic, measure the inside floor before you pay, and cut one side low if your cat is older or stiff.
How do I wash a litter box that is too big for my bathtub?
Empty it into bags first, not down the drain. Stand the box on its end in the tub or shower and wash one half at a time. The sources disagree on soap: AAHA says hot water alone, Cornell allows a gentle detergent. Rinse until no soap smell is left, then let it dry before refilling.
Next step. Give the cat measuring tool one number, your cat’s length, and it returns the shortest box to buy.
Sources
- AAFP and ISFM, “Guidelines for Diagnosing and Solving House-Soiling Behavior in Cats,” Journal of Feline Medicine and Surgery, 2014, journals.sagepub.com, read Oct 16, 2026.
- AAHA and AAFP, “2021 Feline Life Stage Guidelines: general litter box considerations,” aaha.org, read Oct 16, 2026.
- Cornell Feline Health Center, “Feline behavior problems: house soiling,” vet.cornell.edu, read Oct 16, 2026.
- Cornell Feline Health Center, “Feline lower urinary tract disease,” vet.cornell.edu, read Oct 16, 2026.
- Grigg, Pick and Nibblett, “Litter box preference in domestic cats: covered versus uncovered,” Journal of Feline Medicine and Surgery, 2013, PubMed, read Oct 16, 2026.
- American Veterinary Society of Animal Behavior, “What does the science say about cats and covered litter boxes?,” avsab.org, read Oct 16, 2026.
- IRIS USA, “XL Open-Top Cat Litter Box with Shield,” irisusainc.com, read Oct 16, 2026.
- NE14 Pets, “Jumbo Cat Litter Box,” ne14pets.com, read Oct 16, 2026.
- IRIS USA, “XX-Large Side Entry Cat Litter Box, Navy,” irisusainc.com, read Oct 16, 2026.
- Petmate, “Petmate Giant Litter Box,” petmate.com, read Oct 16, 2026.
- IRIS USA, “Hooded Cat Litter Box, Jumbo,” irisusainc.com, read Oct 16, 2026.
- Van Ness Pet Products, “High Sides Giant Cat Litter Box (CP3HS),” vannesspets.com, read Oct 16, 2026.
