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Too few boxes is the most common cause of cats going outside the box — and the fix is cheaper than new carpet. Enter your cat count below to get the recommended number of boxes, the size to buy, and roughly how much litter you will use each month.
The n+1 rule
One box per cat, plus one extra. So one cat needs two boxes, two cats need three, and so on. Spread them across rooms and floors rather than side by side — boxes next to each other count as one location to a cat. Each box should be about 1.5× your cat’s body length; most cats prefer large open boxes with 2–3 in (5–7 cm) of unscented clumping litter.
How much litter per month?
| Cats (with n+1 boxes) | Litter per month | Notes |
|---|---|---|
| 1 cat, 2 boxes | 15–25 lb (7–11 kg) | Clumping, scooped daily with weekly top-ups |
| 2 cats, 3 boxes | 25–40 lb (11–18 kg) | Most common multi-cat setup |
| 3 cats, 4 boxes | 35–60 lb (16–27 kg) | A bulk bag or subscription starts paying off |
| 4 cats, 5 boxes | 45–80 lb (20–36 kg) | Consider boxes on every floor |
Non-clumping, crystal and pellet litters are changed differently — follow the maker’s guidance. Scooping daily is the single biggest factor in keeping cats using the box.
FAQ
Where should I put litter boxes?
Quiet, accessible spots on each floor with an escape route — not next to food and water, laundry machines or dead ends. Kittens and senior cats need low-sided boxes they can step into.
My cat stopped using the box — what now?
Add and clean boxes first, then see your vet promptly — urinary issues are common and can be urgent, especially straining or crying in male cats. This page is general information only, not a diagnosis.
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