๐Ÿงบ Cat Litter & Tray Planner

Work out how many litter trays your household needs, the smallest size that suits your cat, and the litter and money the trays will use a month โ€” with the scooping and hygiene rules vets recommend.

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A โ€” Your household and trays
Trays you should have
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The n+1 rule, tray sizing and the litter maths explained

Number of trays. One tray per cat, plus one extra โ€” so a single cat household should have two trays, and two cats need three. The extra tray stops one cat guarding the resources; put them in different places, because several trays side by side count as one territory to a cat. The AAFP/ISFM and Ohio State guidance behind this card says the same thing.

Size beats brand. A tray should be about 1.5 times the length of the cat from nose to base of tail, so an average 45 cm cat needs roughly 68 cm of usable length. Most trays sold in shops are 50 cm or less โ€” which is why a plastic storage box, with a doorway cut into one side, is often the best litter tray in the house. The cat must be able to stand fully and turn around.

Litter depth and type. Around 3โ€“5 cm (about 2 in) of a fine, unscented, clumping litter suits most cats; deeper if your cat digs, shallower for kittens and arthritic seniors. Non-clumping litter is safer for kittens who taste it, but it must be changed completely every week. Whatever you choose, change the type gradually over a week or two or the cat may stop using the tray.

Hygiene that prevents problems. Scoop at least once a day, twice in a multi-cat home. Wash the tray weekly with mild unscented soap or hot water and dry it before refilling โ€” avoid strong disinfectants, citrus and ammonia smells, which cats read as a reason to go elsewhere. Cover trays are usually a mistake: they trap smells, heat and ammonia. Never put a litter tray next to food or water, and keep it quiet and easy to reach.

When a cat stops using the tray. See a vet first, same day if there is straining or blood: bladder inflammation and blockages are common, painful and, in male cats, quickly fatal. Only when illness is ruled out is it a behaviour question โ€” then check the n+1 rule, tray size, litter type, cleanliness, location and whether a new cat or a new baby has changed the house.

The estimate. Litres per fill are the tray area multiplied by the depth. Litter weight uses typical bulk densities (clumping clay about 0.85 kg/litre, non-clumping about 0.6, wood pellets about 0.65, tofu about 0.55, silica about 0.5) โ€” check the bag, brands vary. Monthly use adds a scoop-and-top-up allowance of 1.5 litres per tray per week for litters changed fortnightly or less often. Sources: 2021 AAHA/AAFP Feline Life Stage Guidelines, AAFP/ISFM house-soiling and environmental needs guidance, Ohio State Indoor Pet Initiative. Checked 4 October 2026. โ€” Information only, not veterinary advice.