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Danny's Cats

Litter and hygiene

Litter box size rule

Also called 1.5 times rule

Updated

What is the litter box size rule?

The litter box size rule says a box should be at least one and a half times your cat's length, measured from the nose to the base of the tail. The AAFP and ISFM house-soiling guidelines and Battersea both give the 1.5 times figure, and Battersea warns that many trays labelled large are still too small for adult cats.

How do you measure your cat for a litter box?

Measure along the back from the tip of the nose to where the tail starts, leaving the tail out, then multiply by 1.5. A cat 18 inches long needs a box at least 27 inches long. Compare that with the inside length of the box if you can find it, since walls and rims make the outside figure larger than the floor.

Where does the 1.5 times rule come from?

The AAFP and ISFM guidelines recommend a rectangular box 1.5 times the cat's length from nose to base of tail, and say that in general bigger is better. They cite a study in which adult cats preferred a box 34 by 15 inches (86 by 39 cm) over a smaller one.

That study, published in the Journal of Veterinary Behavior in 2014, gave 74 cats in 43 households a regular box and a larger one. The large boxes were chosen more often, and the authors concluded that most cats prefer a larger box than is typically available to them.

What if no litter box is big enough?

The AAFP and ISFM guidelines suggest looking beyond the pet store: concrete mixing trays, sweater boxes and under-bed storage containers can make suitable boxes. Battersea says to check the measurements rather than the label.

What to look for

  • A published length you can check against your cat
  • Inside measurements, where the maker gives them
  • Room to stand, turn around and dig, as Battersea puts it

Trusting the word large

Battersea warns that many trays labelled large are still too small for adult cats. Measure your cat and compare numbers, not names.

Questions about litter box size rule

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

A litter box for a large cat should be at least one and a half times the cat's length from nose to base of tail, according to the AAFP and ISFM guidelines and Battersea. Cornell adds that overweight and large cats need bigger boxes. Our article on where to put a litter box compares what six authorities say on size, number and depth.

Does a bigger litter box really help?

A bigger litter box does seem to help, judging by what cats choose. In a 2014 study in the Journal of Veterinary Behavior, cats in 43 homes chose a larger box over a regular one more often, and the authors concluded most cats prefer a larger box than they usually get. The AAFP and ISFM guidelines put it simply: bigger is better.

Where this comes up

Sources