The recommended dimensions for a litter box should be one and a half times the length of the cat from nose to the base of the tail. For kittens and smaller cats, a box measuring around 16 by 12 inches is typically sufficient. Adult cats generally require a larger box, about 20 by 15 inches or more, to accommodate their size comfortably. Additionally, the box should have sides low enough for easy entry for kittens and older cats, but high enough to prevent litter spillage. Ensuring proper dimensions helps promote consistent use and comfort.