The litter box: setup, litter and cleaning

Using a litter box is natural for most cats. Kittens learn it very early, usually by watching their mother, so they do not need toilet training the way a puppy does. Cats that go outside still need a box in the house.

A good box set-up prevents stress and unwanted behaviour such as peeing outside the box. The 2014 AAFP and ISFM guidelines on house-soiling give two advice points that apply to every case: make the litter box as good as it can be, and meet the cat's wider needs (a safe place, food and water, play, good contact with people, and a scent-friendly home).

Peeing and pooping outside the box is one of the most common reasons cats end up in a shelter, so getting the box right early is worth the effort. A dirty box can be enough on its own to make a cat go elsewhere in the house. Clean the box well before looking for other causes.

The usual advice is one box per cat plus one extra, so two boxes for one cat and three for two cats. The extra box is a spare and gives the cat a choice, for example when one box is in use, blocked by another cat or not liked. Some cats like one place for urine and another for faeces, which is a second reason that one cat can use two boxes. A few charities say at least one box per cat is the minimum and the extra box is a bonus.

The rule is a rule of thumb rather than a proven number. A literature review calls the evidence weak and says it was first described in 1996. The AAFP and ISFM guidelines call it a historical rule of thumb and not an absolute requirement, and a behaviourist at a cat charity says it is widely used but not based on hard evidence. What the guidelines do agree on is to offer several boxes in several places, not one box in one place.

Put boxes in different spots so that one cat cannot guard them all. Two boxes side by side count as one big box to a cat. If boxes must be near each other, their openings should not face each other. In a home with more than one floor, put a box on every floor, so the cat never has far to go. This matters most for kittens and older cats. In a multi-cat home a cat may refuse a box another cat has just used. Scoop more often and add boxes if you see this.

The box should be about 1.5 times the length of the cat, measured from nose to the base of the tail. Bigger is better. The cat must be able to walk in, turn around without touching the sides, dig, scratch and stretch out. Many boxes sold as large are still too small, and most standard boxes are too small for a fully grown cat.

Research supports bigger boxes. In a study of 74 housebound cats in 43 homes, most cats used a large box (86 cm long) more than regular boxes. A comparison found cats preferred a longer box (86 cm) to a short one (56 cm). A large plastic storage container makes a good, cheap box. For a big cat, cut a low opening in one or two sides and file or sand every edge so nothing is sharp.

Start a tiny kitten with a small, low-sided tray and move to a full-size box as it grows. A box the kitten can grow into also works, as long as it can climb in easily.

Studies do not show that cats overall prefer one or the other. In a study of 27 cats, with large boxes, daily scooping and clumping litter, 19 cats had no preference, 4 chose a covered box and 4 chose an open one. None of the six large cats (6 kg or more) chose the covered box. In a group study in a cattery, more urine was found in open boxes than in covered ones (98 g against 77 g per day), but the study measured the whole group and cannot show what each cat liked. The authors note a dirty box may put cats off more than the lid itself.

Reasons many vets and charities lean to open boxes: covered boxes trap smell and ammonia, so they need cleaning more often; dirty litter out of sight is easy to forget; a large cat may not have room to turn; a covered box with one exit lets another cat ambush the user; and a swing door can scare or block some cats. Reasons some cats and owners prefer a covered box: it feels private for a timid cat and keeps litter and smell more contained. A covered box is accepted only if it is roomy and kept very clean.

The simple answer from the guidelines and charities: try both. Offer one of each and see which one your cat uses. If the cat avoids a covered box, switch to an open one. Open boxes also suit kittens, older cats and cats with back pain. Top-entry boxes are generally not advised for older cats or cats that move with difficulty.

Choose a quiet place with little foot traffic that is always easy to reach. Do not put the box near food, water or the bed. A cat does not want to toilet where it eats, and research on a colony of free-living cats found they avoided toileting in feeding areas. Avoid noisy places: next to a washing machine, dryer or boiler that can start suddenly. A cold basement or a dark, cramped corner is also not ideal.

Choose a spot where the cat can see people or animals approach and has more than one way out. Avoid dead ends and hidden spots where it can be trapped by another cat, and avoid spots next to a full-length window or a cat flap. If the box sits in a bathroom or closet, make sure the door cannot swing shut and trap the cat in or out. Keep the position predictable: cats feel settled when food, water and the box are always in the same places. A night light near the box helps in the evening, especially for older cats. If a cat toilets in one spot repeatedly, adding an extra box in that spot, temporarily or for good, is a simple fix.

Most cats prefer a soft, fine-grained, unscented litter with little dust that feels like sand under the paws. Many cats dislike strong scents, dusty litter, deodorants and box liners. Perfumed litter has no benefit for the cat and can put it off using the box. No type is best for every cat. Cats often prefer what they used as a kitten. To find out, put two or more litters side by side in separate boxes and see what the cat picks.

Clumping clay (bentonite) is the classic type that most cats accept. Urine forms a hard lump you can scoop out, so you only replace the whole filling now and then. Downsides: it can be dusty, heavy and messy, and some clumping clays contain crystalline silica dust. Dust from mineral litter can be breathed in and a harmful effect cannot be ruled out. Clumping litter is for adult cats; very young kittens are not always ready for it. Non-clumping clay is often the cheapest and absorbs urine, but it is heavy and dusty, turns muddy when wet and must be changed completely and often (at least twice a week for the box). The price per kg says little about real cost, since cheaper litter is replaced more often.

Silica gel (crystals) is light, very absorbent and keeps smell down for a long time, so mainly the droppings need scooping. Downsides: it costs more, stirring is needed so urine does not pool, it rustles, can stick in long fur and scatter, and is harmful if swallowed. Some cats dislike the feel. Wood (pellets or fibre) has little dust, is light and absorbs smell well, and most is compostable where local rules allow. Downsides: it often does not clump, may need a special tray, and some cats find hard pellets rough on the paws compared with sand-like litter.

Recycled paper is soft and low in dust, a reasonable choice, but it has to be changed often and gets kicked out of the box easily. Other plant-based litters (for example corn, wheat, straw or plant fibre) often absorb smell well and are biodegradable. Downsides: they can cost more and not all of them clump, so cleaning can be more work. Once a cat likes a litter, stay with it. Switch slowly over one to two weeks by mixing the new litter into the old, or offer it in a separate box first. A sudden switch, or buying whatever is cheapest that week, can make a cat avoid the box. Long-haired cats may carry grains in the fur and paws: a mat at the exit helps, and a heavier litter may do better than one that is too light.

Add enough litter for the cat to dig and bury. The numbers differ between sources, from at least 3 cm up to 5 cm, with some saying a thin layer of 2.5 to 5 cm and a few higher. The practical range is about 3 to 5 cm. Cats vary in what they like. Some enjoy deep litter, some do not like to bury their paws, and long-haired cats may prefer less. If your cat soils soft surfaces it may want more litter; if it soils hard floors it may want less.

Too deep makes an uneven surface that some cats dislike. More litter does not mean you can scoop less often. A cat that passes a lot of urine, for example from a medical condition, may need deeper litter to soak it up. That is also a reason to ask the vet. Clumping litter needs enough depth to form stable clumps. Broken clumps make the rest of the litter dirty.

Scoop out clumps and droppings at least once a day. Some sources advise twice a day, and you can do it in the morning because cats are most active at night. In a cattery, boxes were scooped twice a day. Scooping every day is linked to fewer problems: a study found house-soiling more often in boxes that were not scooped daily.

Replace all the litter and wash the box regularly. How often depends on the litter and how many cats share the box: about weekly for clay or non-clumping litter, and every two to four weeks for clumping litter that you scoop daily. The AAFP and ISFM guidelines say to wash the box every one to four weeks. Change sooner when the litter smells, is wet in the bottom or the clumps have broken up into the rest of the litter. Wash the empty box with hot water and a mild, unscented soap (washing-up liquid is fine), rinse well and dry it before adding fresh litter. Wash your hands afterwards.

Avoid strong chemicals, ammonia products, strong disinfectants, citrus oils and strongly scented cleaners. They smell strong to a cat, can put it off and may be toxic. Phenol disinfectants are toxic to cats. A university cat health centre also advises against ammonia and vinegar cleaners because they smell like urine. If bleach is ever used, rinse very thoroughly and let the box dry fully. Plastic absorbs smell over time. If a box still smells after a good wash, replacing the box is the answer.

To keep smell down: scoop daily, change the litter on time, and keep a covered box especially clean. A thin layer of baking soda on the bottom of the empty box also absorbs odour and does not bother the cat. A carbon filter in a covered box helps only if the filter is replaced. Clean accidents on the floor quickly with an enzymatic or biological cleaner. It removes the smell that would tell the cat to go back to the same spot. Never punish a cat for an accident.

Used litter goes in the household waste (residual waste). Do not put it in the garden compost or the green bin: home compost may not get hot enough to kill the Toxoplasma parasite, and in some places litter in the green bin is not allowed. Do not flush it down the toilet: clumping and plant litter swell and clog pipes, and droppings can reach surface water. Waste rules differ by place, so see the country block too.

Kittens start to explore litter from about 3 to 5 weeks, start to rake at loose material at about 30 days, and use a box from about 5 to 7 weeks. By about 8 weeks most are house-trained. If you have a kitten from 8 weeks old, assume it can already use a box. A kitten does not need to be shown by moving its paws through the litter; offering an easy-to-reach box is enough.

Give a young kitten a box with low sides it can step into easily, and keep it close, so the kitten does not have far to walk. Add one or two extra boxes in the first weeks after adoption, and move up to a larger box as it grows. In the first days, keep the kitten in one room or a small area, with the box in a quiet spot well away from food and bed. Widen its space once it reliably uses the box. Take it to the box after meals, after waking and after play.

Add a little of the kitten's old litter to the fresh litter. The familiar smell encourages it to use the box. Use the same litter the kitten had before. Accidents are normal while a kitten is learning. Do not punish them.

Choose a box with a low entry so the cat can walk in without jumping. You can cut down one side of a plastic box, checking the edges are smooth. Large, shallow boxes can suit a stiff cat best. Low entry also helps cats with joint pain. Put a box on the level where the cat spends most of its time, so it does not need stairs. Extra boxes close to sleeping areas and a night light help. Check the way to the box too: slippery floors, a wobbling mat, gates and stairs can make a good box hard to reach. Open boxes usually suit older cats better than top-entry or covered ones.

An older cat that starts missing the box often has pain, such as arthritis, or an illness such as kidney problems, diabetes or a urinary problem. This needs a vet check. Senior cats should have a check-up at least every six months.

Once a box is in a good place, do not move it around. Frequent moves confuse and stress the cat. When a cat is new to the house, show it where the box is as soon as it arrives. When you do need to move it, do it gradually: about 1 cm per day, once the cat has used the box reliably for weeks. Keep the old and the new place both available for a while. Once a cat is using a box in a new place, leave it there for at least two weeks before changing anything else.

If you are trying changes because a cat avoids the box, change one thing at a time, such as place, litter or box, so you can tell what worked. Keep a familiar box available while testing a new one.

A self-cleaning box uses a sensor to notice that the cat has left and then combs or sifts the waste after a delay. Some connect to the plumbing to wash the litter. They keep the litter cleaner and some cats take to them without any trouble. Others dislike the noise, movement or smell, or the unstable feel, and avoid the box. No study was found that tests them against ordinary boxes.

Vets and charities differ: some advise against them for nervous or easily startled cats, and some say their features matter less than space and easy access. A sensible way is to keep a familiar box next to it. If the cat starts avoiding the automatic one, go back to a plain box.

Cats are the only animals that shed Toxoplasma eggs (oocysts) in their droppings, so litter can carry them. A cat usually catches the parasite by eating infected prey such as rodents or birds, and sheds oocysts for only a few weeks after a first infection. Most cats are not made ill by it. For most healthy people, a Toxoplasma infection goes unnoticed or feels like mild flu. It is a concern mainly in pregnancy and in people with a weakened immune system, because the parasite can harm an unborn baby or cause serious illness. After an infection a person is usually immune.

The simple advice from public-health sources: if you are pregnant, or your immune system is weakened, let someone else clean the litter box. If no one else can, scoop it every day, wear disposable gloves, and wash your hands well with soap and water afterwards. Daily scooping lowers the risk because the oocysts need time after they are shed before they can infect. Sources give one day, 48 hours and one to five days. Indoor cats that do not hunt and are fed commercial food rather than raw meat are unlikely to carry Toxoplasma. Kittens and young cats are more likely to shed it, so it is better not to bring a new kitten or a stray into the house while pregnant or trying to conceive.

You do not have to give up your cat. The parasite is not passed on by stroking the cat, and the fur is very unlikely to carry it. Wash your hands after petting, especially before eating, and keep the cat off kitchen counters and the table. Cat litter is not the only route: raw or undercooked meat, unwashed vegetables and fruit, and soil when gardening matter too, so wear gloves in the garden and wash produce. Some owners wonder if years with cats mean they are already immune. Not necessarily: people can live with cats for years without ever being infected, and the risk is the same in every pregnancy. A blood test can show whether you have had it. Ask your doctor or midwife about it when you are trying to conceive or are pregnant. Do not flush cat droppings or compost litter: both can bring oocysts to water or soil.

Peeing or pooping outside the box is often a health problem first. Causes include urinary infection or stones, cystitis, kidney disease, diabetes, an overactive thyroid, arthritis, constipation and pain. Rule out a medical cause with the vet before changing the set-up. If the vet finds nothing, look at the box itself: number, size, place, litter and cleanliness. Stress, a new pet or person, a move or conflict with another cat can also play a part. Keep a diary and floor plan of where the cat goes; that shows patterns.

Spraying small amounts of urine on upright surfaces is marking and has a different cause and approach. See our page on peeing outside the litter box for causes and what helps. Punishment never helps. Shouting, rubbing the cat's nose in it or dragging it to the box makes the cat afraid and can make the problem worse.