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By Jason Feng, Founder & Researcher. See how this review was researched.
Quick answer
By floor area, the CATLINK Scooper SE Lite is the smallest self-cleaning box among the twelve current models we compared, at roughly 450 square inches and $219. The CATLINK Scooper SE is next at about 495, then the Litter-Robot EVO at about 501.
Small is not one number. The PETKIT Purobot Crystal Duo stands only 13.14 inches tall, the lowest profile sold, but it runs 32.20 inches deep. Measure the floor and the height separately before you buy.
Table of contents
- What smallest actually means
- The footprint ranking
- Height, the second smallness
- The entry height nobody lists
- What small costs you inside
- Apartment constraints that beat the footprint
- Bathroom placement and moisture
- The narrow-deep trap
- Small boxes for small cats, and the exception
- Our verdict
- How we researched this
- Sources
What smallest actually means
Four numbers describe how small a litter box is, and vendors publish them inconsistently. Only one is what most people mean.
Floor footprint is width times depth. That is the space you give up permanently, and it decides whether a box fits a closet, a bathroom corner, or the gap between a toilet and a wall.
Height decides whether it fits under a shelf, inside a cabinet, or beneath a window sill.
Entry height is the rise a cat has to take. It does not affect whether the box fits, but it decides whether the cat uses it, and it is the number small boxes most often get wrong in the wrong direction.
Interior volume is what the cat gets. This is where small boxes pay for their footprint, and it is the number vendors promote hardest when it is generous.
The ranking below sorts by floor area first, then corrects for the other three.
The footprint ranking
Every figure is from the manufacturer’s own product or support page, captured on 2026-10-27 through a US egress. The area column is arithmetic on those figures.
| Model | Footprint (W x D) | Floor area | Height | Entry height | US price on 2026-10-27 |
|---|---|---|---|---|---|
| CATLINK Scooper SE Lite | 20.98 x 21.45 in, axis order not stated | about 450 sq in | 23.58 in | [DATA NOT VERIFIED: not published on the SE Lite page] | $219 |
| CATLINK Scooper SE | 23.58 x 20.98 in | about 495 sq in | 21.46 in | 9.45 in | $259 |
| Litter-Robot EVO | 20.6 x 24.3 in | about 501 sq in | 27.6 in | 14.85 in opening | $599 |
| PETKIT Purobot Max 3 | 24.4 x 21.2 in | about 517 sq in | 21.7 in | 8.03 in | $399.99 |
| Petlibro Luma | 23.3 x 22.5 in | about 524 sq in | 28.1 in | 17.4 in entrance | $599.99 |
| PETKIT Purobot Max Pro 2 | 25.86 x 21.18 in | about 548 sq in | 23.74 in | 10.03 in | $499.99 |
| Neakasa M9 | 26 x 22 in | about 572 sq in | 25.7 in | 10 in | $389.99 |
| Litter-Robot 4 | 22 x 27 in | about 594 sq in | 29.5 in | 12 in to entry | $699 |
| Litter-Robot 5 | 22 x 27 in | about 594 sq in | 29.9 in | 15.75 in opening | $799 |
| CATLINK Scooper Open-X | 25.6 x 23.6 in | about 604 sq in | 27.5 in | 13.8 in | from $169 |
| PETKIT Purobot Crystal Duo | 32.20 x 19.96 in | about 643 sq in | 13.14 in | 7.08 in | $199.99 |
| PETKIT Purobot Ultra | 20.94 x 32.20 in | about 674 sq in | 24.09 in | 10.43 in | $799.99 |
Three notes before you use the table.
The Scooper SE Lite’s own page lists its dimensions as a three-number string without naming the axes, and the middle figure does not match the SE’s published width. I have ranked it first because every plausible reading of that string puts it under 500 square inches, but the exact orientation is unconfirmed. If you are buying for a tight alcove, measure the SE instead: its page breaks the numbers out by name.
The price column is the figure shown on the manufacturer’s page on the date captured, and several are promotional rather than list. The CATLINK SE Lite shows $219 against a $359 regular price, the PETKIT Purobot Max 3 shows $399.99 against $499.99, and the Neakasa M9 shows $389.99 against $549.99. Budget for the higher number if you are not buying this week.
The CATLINK Open-X row carries $169 for the single-cat configuration and $199 for the multi-cat, which is a configuration difference rather than a sale. It is also the widest at 25.6 inches, so it does not belong in a narrow slot.
Height, the second smallness
If your constraint is a shelf, a counter overhang, or a cabinet interior, the ranking inverts.
The PETKIT Purobot Crystal Duo is 13.14 inches tall. That is not a compact version of a rotating drum: it is a low tray design that uses PETKIT’s own crystal litter set, and the company states it is compatible with nothing else. It is the only machine here you could slide under a low bench.
The CATLINK Scooper SE and the PETKIT Purobot Max 3 both land near 21.5 inches, which fits under a standard 30-inch counter with room to spare. The Litter-Robot EVO is 27.6 inches, the Litter-Robot 5 is 29.9, and the Litter-Robot 4 is 29.5. Those three will not go under a counter at all.
That gap is why a small box and a short box are different purchases. A Litter-Robot EVO occupies less floor than a Litter-Robot 4 and still stands 27.6 inches tall, because the globe geometry does not compress vertically. Our Litter-Robot 4 dimensions guide covers the clearance math for that family, including the space the bonnet needs to open.
One rule applies to every model: measure the working height, not the resting height. A machine that stands 21.7 inches may need another six inches above it to lift a lid or remove a cylinder. The number on the spec sheet is the parked height.
The entry height nobody lists
Here is the number that separates a small box your cat will use from one it will not.
The PETKIT Purobot Max 3 publishes an entry height of 8.03 inches and markets it as a low, wide entry for all breeds and ages. The CATLINK Scooper SE publishes 9.45 inches high by 8.38 inches wide. The Neakasa M9 publishes 10 inches, calling it easy for kittens and senior cats. The Litter-Robot EVO puts its opening at 14.85 inches, and the Litter-Robot 4’s entrance sits 12 inches up with a 6.9-inch step in front of it.
Read those as a spread from 8 to 14 inches of climb. For a young, mobile cat, all of them are trivial. For a 14-year-old cat with arthritis, the difference between 8 inches and 14 is the difference between a box that gets used and a rug that does not.
Two caveats on comparing these numbers. Vendors do not agree on what "entry height" measures: some mean the lip of the opening, some mean the top of a threshold, and some mean the first step. And a low entry is not automatically better, because a low entry on a rotating drum usually means a shallower litter bed, which means more tracking out the front.
If the cat is the constraint rather than the room, our guide to automatic boxes for senior cats works through ramps, steps, and low-entry designs in more detail.
What small costs you inside
Every inch of footprint you remove has to come from somewhere. In this category it comes from four places, and you should know which one you are accepting.
| Cost | Small-box figure | Reference machine |
|---|---|---|
| Waste drawer | 7 L, empty every 7 to 11 days for one cat | CATLINK Scooper SE Lite page, CATLINK FAQ |
| Drum volume | 65 to 70 L | CATLINK Scooper SE and SE Lite |
| Cat weight ceiling | 19 to 22 lbs | Litter-Robot EVO, CATLINK line |
| Litter bed | shallower by design at a low entry | PETKIT Purobot Max 3 |
Waste drawer capacity shrinks first. CATLINK’s own FAQ suggests emptying every 7 to 11 days for a single cat. A small box in a two-cat home means emptying twice a week, which is a real ongoing cost even when the purchase price is low.
Drum volume shrinks second, though less than the footprint gap suggests. The CATLINK figures of 65 to 70 L sit against 76 L for a PETKIT Pura Max 2, because a vertical drum is an efficient shape.
Cat weight ceilings shrink third, and this is the constraint people miss. The Litter-Robot EVO is rated to 19 lbs, the CATLINK boxes to 22 lbs, the Litter-Robot 4 to 25 lbs, and the Litter-Robot 5 to 30 lbs. A 20-pound cat that fits a Litter-Robot 4 is over the published range on an EVO, and over-range use is where false sensor readings start.
Litter capacity shrinks last, and it matters least. A smaller bed means more frequent top-ups, not a different experience.
Apartment constraints that beat the footprint
In a small apartment the binding constraint is rarely the floor. It is usually one of five things.
The door swing. A machine in a bathroom needs the door to open past it, and a 24-inch-deep box in a 30-inch-wide bathroom leaves six inches of swing. Measure with the door open.
The outlet. Every machine here is corded. A box placed for floor fit and not for outlet proximity means an extension cord across a walkway, which is a trip hazard regardless of brand.
The path in. A shipping carton is much larger than the machine, and it has to pass the hallway corner and the front door. Check the narrowest opening on the route against the carton, not the product.
The noise. A machine in a studio cycles at night. Published figures put the PETKIT Purobot Max 3 at 35 dB and the Neakasa M1 at 50 dB or under, a meaningful spread in a room where you sleep.
The smell path. A box in a small bathroom concentrates odor, and the moisture question below removes that room from consideration anyway. Our enclosure buying guide covers what closed furniture solves and what it makes worse.
Bathroom placement and moisture
Worth separating out, because it interacts badly with the small-apartment problem.
Whisker’s placement guidance recommends avoiding the bathroom, on the grounds that moisture can damage components. That rules out the room most renters would pick first. PETKIT’s published constraints are different: hard flat floor, 5 cm from the wall, nothing near the entrance, no direct sunlight on the entrance sensor. Moisture is not on PETKIT’s list.
The practical compromise for a small apartment is a hallway, a laundry room, or a closet with the door removed. A closet adds a height constraint, which pushes you toward the 21-inch band rather than the Litter-Robot family.
The narrow-deep trap
The most common measurement mistake in this category is treating a narrow box as a small box.
The PETKIT Purobot Ultra is 20.94 inches wide, which sounds excellent, and 32.20 inches deep, the deepest machine in the table. Its floor area is the largest of the twelve. It fits a narrow slot and ruins a shallow one. The Litter-Robot 4 and 5 are the reverse case: 22 by 27 fits a wall run but not a corner nook.
So measure three things: the width of the slot, the depth available, and the height above. A box that fails any of the three does not fit, and no configuration change rescues it. The pattern to watch for is a machine deeper than 24 inches, because that is the depth of most standard closets and alcoves.
If the intended spot is a corner, note that none of these machines is designed to sit at an angle, and Whisker asks for about an inch of clearance from the wall. A corner also needs the waste drawer to pull out toward open floor.
Small boxes for small cats, and the exception
There is a version of this question where the cat is small and the box should be too. The CATLINK boxes are rated from 3 lbs 8 oz against the Litter-Robot 4’s 3 lbs, a difference that matters less than it looks: both numbers describe where automatic mode becomes safe, and both companies recommend supervised or manual operation below it. CATLINK adds an age floor of 3 months.
The PETKIT Purobot Crystal Duo is the exception, and it is a different product category wearing the same label. It is 13.14 inches tall, 32.20 inches deep, and rated for cats over 3.3 lbs with no published upper limit. It uses a disposable crystal tray rather than clumping litter, PETKIT states it is compatible only with its own crystal litter set, and each tray is rated for up to 45 days. That is a genuinely small box in height and a genuinely large one in depth, with an ongoing consumable cost that the $199.99 price does not include.
If your constraint is a low clearance under furniture, it is the only option in the table. If your constraint is floor space, it is near the bottom.
For the broader field, including boxes that trade footprint for capacity, our roundup of automatic litter boxes covers the category by use case rather than by dimension.
Our verdict
Buy the CATLINK Scooper SE if floor area is the binding constraint and the cat is under 22 lbs. At about 495 square inches and 21.46 inches tall it is the smallest machine with a fully published dimension set, and $259 is a third of what the Litter-Robot 4 costs.
Buy the Scooper SE Lite instead only if you are willing to measure it yourself. Its listed dimensions put it marginally smaller and its price is $40 lower, but the axis order is not stated on the page. For a tight alcove that is an unnecessary risk.
Buy the PETKIT Purobot Max 3 if the constraint is height rather than floor. At 21.7 inches tall with an 8.03-inch entry it is the easiest machine in the table for an older cat to walk into, and $399.99 with a 7 L bin is a reasonable middle.
Buy the Litter-Robot EVO if you want the Litter-Robot ecosystem in less floor space and your cat is under 19 lbs. It is 25 percent smaller than the Litter-Robot 5 by Whisker’s own description, and it gives up the integrated carpet tray to get there.
Do not buy for a cat over the published weight range, and do not buy on footprint alone. The entry height decides whether the box gets used, and whichever of width, depth, or height is smallest in your space decides whether it fits.
If price is the real constraint rather than size, our guide to cheap automatic litter boxes covers what the $200 to $450 band gives up. If two cats share one small box, our multi-cat guidance explains why the capacity math changes before the footprint does.
How we researched this
- Every dimension, entry height, capacity, weight limit, and US list price in this article was read from the manufacturer’s own product or support page on 2026-10-27, fetched through a US egress with an en-US language header. The source list below is the exact set of pages used.
- Floor area is arithmetic on the published width and depth figures, rounded to the nearest square inch, and is presented as a calculated value rather than a vendor specification. Where a vendor did not state the axis order, the row says so.
- Where a manufacturer does not publish a figure, the cell is marked rather than filled with an estimate from a similar model.
- The bathroom moisture guidance and the carpet and clearance requirements are manufacturer statements about their own products, not general advice we originated.
- This is a research-based review. Specifications come from manufacturer documentation, with owner-reported failure patterns aggregated across public reviews and community threads.
Read more about how we research and our affiliate disclosure.
Sources
Fetched on 2026-10-27 through a US egress with an en-US language header:
- https://www.catlinkus.com/products/catlink-smart-litter-box-scooper-se
- https://www.catlinkus.com/products/catlink-smart-litter-box-scooper-se-lite
- https://www.catlinkus.com/products/catlink-self-cleaning-litter-box-scooper-open-x-single-cat
- https://www.catlinkus.com/products/catlink-self-cleaning-litter-box-scooper-pro-basic-set
- https://www.litter-robot.com/litter-robot-4.html
- https://www.litter-robot.com/litter-robot-5.html
- https://www.litter-robot.com/litter-robot-evo.html
- https://petlibro.com/products/luma-smart-litter-box
- https://www.petkit.com/products/purobot-max-3-automatic-cat-litter-box
- https://www.petkit.com/products/purobot-max-pro-2-automatic-cat-litter-box-with-ai-camera
- https://www.petkit.com/products/purobot-ultra
- https://www.petkit.com/products/purobot-crystal-duo-cat-litter-box-with-camera
- https://neakasa.com/products/neakasa-m9-smart-litter-box
- https://neakasa.com/products/neakasa-m1-cat-litter-box