A cat that does not fit is the most common reason one of these comes back. The published weight limits are only half the problem: the other half is room to turn around, which nobody publishes at all.
Size limits checked
| Model | Max cat | Entry opening | Step-up | Verdict for a big cat |
|---|---|---|---|---|
| Litter-Robot 4Whisker | not published | 40 x 40 cm | not published | The largest opening in the category and no stated ceiling. The best of the three, with the caveat that "no limit published" is not the same as "tested to a limit". |
| Purobot UltraPETKIT | 10 kg | not published | 26.5 cm | Lowest step-up, which helps a heavy older cat, but a hard 10kg ceiling that a large male can pass. |
| Scooper Luxury Pro XCATLINK | 10 kg | 33 x 27 cm | 35.5 cm | Smallest published opening and the highest step-up. The weakest fit for a large or elderly cat of the three. |
Measure your cat before you shop. Nose to the base of the tail, then multiply by 1.5. That is the internal length the box needs. For most cats over about 6kg the answer is longer than a supermarket tray, and for a Maine Coon or a large Ragdoll it can exceed what the drum-style automatics comfortably offer.
If your cat is over 10kg, both PETKIT and CATLINK have ruled it out in writing and Whisker has declined to say. At that point the automatic category is a gamble, and a large manual tray or a storage tub with a cut entry is the reliable answer. It is not the answer anyone selling litter boxes wants to give, but a big cat with an unsuitable box will simply go elsewhere in the house, and that costs more than the box did.
If you do try an automatic, buy the one with the money-back guarantee. It is the only term in the category that covers a cat deciding no.
The usual guidance is a box at least one and a half times the length of the cat from nose to base of tail, which for a large cat is often 60cm or more. That is longer than most manual trays sold in Australian supermarkets, and it is why owners of big cats end up in the automatic category or buying storage tubs.
Physically, usually. The drum-style boxes have generous chambers and the Litter-Robot 4 has the largest entry opening at 40cm by 40cm. The catch is that PETKIT and CATLINK both state a 10kg maximum, and a large male Maine Coon can exceed that. Whisker publishes no maximum for the Litter-Robot 4 at all, saying only that larger cats fit, which is reassuring and unverifiable in equal measure.
Almost always because it does not have room to turn around and dig, rather than because it cannot get in. A cat needs to circle, scratch, position and cover, and a chamber sized to contain a cat is not the same as a chamber sized to let it behave normally. If your cat stands in the box with its head or tail outside, it is too small.