Many litter tray problems are really size problems. A cat that toilets outside the tray, perches on the rim, or kicks litter across the floor is often telling you the box is too small for its body. This free litter box size calculator takes your cat length and gives you the minimum length and width a tray should have, so you can buy once and buy right.
Cats like room to turn around, dig, and settle in a comfortable position. A tray that forces a cat to crouch half outside the box feels unsafe, and some cats will simply choose the rug instead. Kittens grow fast too, so a tray that fit at four months can be far too small by the first birthday. Checking the size now prevents months of mess and stress.
The tool is simple. Measure your cat from the tip of the nose to the base of the tail, in centimetres, while the cat is standing or lying stretched out. Do not include the tail in the measurement. Enter that number, press Calculate box size, and you will see the minimum tray length and width in both centimetres and inches.
The rule behind the numbers is easy to remember. The tray should be at least one and a half times your cat length from end to end, and at least as wide as your cat is long. So a cat measuring 50 centimetres needs a tray at least 75 centimetres long and 50 centimetres wide. That sounds large, and it is, because most trays sold in shops are smaller than cats actually need.
A worked example makes it concrete. A cat of 46 centimetres needs a minimum tray of 69 centimetres by 46 centimetres, which is about 27 inches by 18 inches. A cat of 60 centimetres, common for large breeds, needs 90 by 60 centimetres. If you cannot find a tray that big, a large plastic storage box with a doorway cut in one side works well and costs very little.
Size is not the only factor, so keep the other basics right as well. Most homes need one tray per cat plus one extra, placed in quiet spots that are easy to reach. Keep trays away from food and water bowls, scoop daily, and wash the tray with mild soap when you change the litter. A big tray that is dirty will still be rejected.
Common mistakes are easy to avoid. Do not buy a covered tray that is smaller inside than an open one, and do not assume a kitten tray will last into adulthood. Measure again after your cat finishes growing, and again if you adopt a second, larger cat. Older or stiff cats also need a low entrance, even in a large tray, so they can step in without jumping.
This calculator gives minimums, not ideals. Bigger is almost always better, as long as the tray still fits your home and your cat can step in easily. It is free, it needs no sign-up, and it runs entirely in your browser, so you can re-check the numbers whenever your cat grows or your home changes.
A few questions come up in almost every home. Covered trays feel private to humans, but many cats dislike the trapped smell and the single entrance, so if you use a cover, make sure the inside space still meets the minimums from this calculator and that the entrance is wide. Kittens need a tray they can climb into easily, so a low entrance matters more than size in the first months, and you should upgrade as they grow. Senior cats with stiff joints need the same low entrance plus a tray placed close to where they sleep, since a long walk to a distant tray causes accidents. If two cats share a home, give each cat its own tray in a different spot rather than one giant tray, because cats value separate toilets far more than humans expect, and the one-plus-one rule prevents most territorial toilet problems.