How to use the litter box count calculator
Enter how many cats live with you, how many floors they actually roam, and how many boxes you keep today. The tool reports how many more you need. Even with a single cat the recommended count starts at two boxes.
The basis is the N+1 rule, one box per cat plus one spare. AAFP and AAHA both carry it in their feline life stage guidance, and that is still the case as of October 2026. Floor access is layered on top: when the number of lived-in floors is higher than N+1, the recommendation rises to match the floor count.
This tool counts boxes only. It does not cover box size, litter type, covered versus open boxes, or scooping frequency. This tool is for reference only and does not replace veterinary care. Contact your veterinarian right away if you notice symptoms or suspect a problem, such as urinating outside the box or straining in the box.
Frequently asked questions
If one cat blocks the entrance, the others cannot use that box. The spare box is meant to reduce that kind of resource competition and the holding behaviour it causes.
Every cat should reach a box without climbing stairs, so when the number of lived-in floors is higher than N+1 the recommended count rises to match the floor count.
Count and size are separate questions. This tool works out the count only and does not cover box size, litter type or whether the box is covered.