How to Get Rid of Cat Litter Box Smell: 9 Fixes That Work

Knowing how to get rid of cat litter box smell starts with knowing where it comes from. The sharp smell is mostly ammonia, made by bacteria breaking down urine left in the box. Perfume and air fresheners only cover it. Here’s how to find your cause and the nine fixes that actually work.

Why Litter Boxes Smell

When a cat pees, urea soaks into the litter, and bacteria turn it into ammonia gas. Scooping removes the clumps but not the bacteria in the litter left behind. That’s why a box can smell soon after you’ve cleaned it.

There’s also a twist that makes the problem easy to miss. The ATSDR, a US public health agency, notes that people can smell ammonia at about 5 parts per million, but that it causes olfactory fatigue. You stop noticing a smell you live with, so visitors often smell your litter box before you do.

The best test is to step outside for a few minutes, then walk back in. If you notice the box, guests certainly do.

Find Your Cause: Quick Troubleshooter

Most litter box smells come from a handful of causes. Match what you’re noticing to the likely cause, then jump to the fix.

The last row matters most. If the smell of your cat’s urine changes, rather than the box smelling stale, the cause may not be the litter at all.

Fix 1: Scoop at Least Once a Day

Daily scooping is the single biggest fix. The AAFP and ISFM guidelines set once a day as the minimum, and twice is better. Every clump you lift removes urine before bacteria have long to turn it into ammonia.

Top up with fresh litter after each scoop so the depth stays steady. My guide on how often to change cat litter covers the full routine.

With two cats, I scoop our Breeze box every day. Our Litter-Robot 4 sifts itself, and I empty its drawer every two to three days.

Where the scooped waste goes matters too. Owners often mention two habits that help: a sealed diaper-pail style bin next to the box, or taking waste straight to an outdoor trash can. An open kitchen bin just moves the smell to another room.

Fix 2: Use a Firm, Unscented Clumping Litter

The litter does most of the odor work. A litter that forms tight clumps lets you lift urine out whole, while soft clumps crumble and leave urine behind. In published test-strip readings, Arm & Hammer Clump & Seal and World’s Best both stayed under the 5 ppm odor threshold after 24 hours.

My guide to the best cat litter for odor control compares litters on ammonia readings, absorbency and clumping.

Fix 3: Do Full Changes and Wash the Box

Scooping leaves bacteria behind, so the whole box needs a reset regularly. The AAFP and ISFM recommend washing the box every one to four weeks. Cornell’s rule is simpler: change the litter often enough that the box looks and smells dry and clean.

Wash with hot water and mild soap only. The AAFP and ISFM advise against strong chemicals and ammonia-based products, and Arm & Hammer warns never to use chlorine bleach. An enzyme cleaner works well for a monthly deep clean. Dry the box completely before refilling.

Fix 4: Replace Old, Scratched Boxes

Plastic boxes don’t last forever. Replace them every 12 to 18 months, because scratches in the plastic hold bacteria that washing can’t reach. That isn’t a vet guideline, but it’s a cheap fix if a clean box still smells.

Run your hand over the bottom of the box. If it feels rough or looks cloudy with scratches, a new box may do more than any cleaner.

Fix 5: Keep the Litter About Two Inches Deep

Thin litter lets urine reach the floor of the box, where it pools and smells. The AAFP and ISFM ask for at least 1.25 inches, and Cornell suggests one to two inches. About two inches gives urine enough litter to soak into and clump.

My guide on how deep cat litter should be explains the numbers and includes a calculator for how much litter your box needs.

Fix 6: Have Enough Boxes for Your Cats

One box shared by several cats fills up fast. The AAFP and ISFM recommend at least one more box than you have cats, in separate locations. More boxes spread the load, so each one stays fresher between cleanings.

My guide on how many litter boxes per cat covers placement as well as numbers.

Fix 7: Give the Box Some Airflow

A box shut in a closet traps ammonia. Ventilation helps, since fresh air dilutes the smell. A spot with a window or good air circulation helps, as long as it’s still quiet and easy for your cat to reach.

Covered boxes are a trade-off here. They hide the box from view but can hold odor inside, where your cat has to breathe it. Cornell notes that most cats prefer uncovered boxes that let odors escape.

Some owners also run an air purifier near the box. It won’t fix a dirty box, but it can help in a small apartment or a room without a window. Put it where the fan noise won’t put your cat off using the box.

Fix 8: Skip Scented Sprays and Deodorizers

It’s tempting to spray over the smell. The AAFP and ISFM note that cats often find scented litters and litter deodorizers offensive, and a cat that dislikes its box may go elsewhere. And bluntly, perfume on top of ammonia smells worse than ammonia alone.

If you want an additive, activated carbon traps ammonia rather than masking it. Litter-Robot’s summary of Neilson’s research reports that cats preferred carbon to baking soda as an odor additive. My guide on whether scented litter is bad for cats covers the research.

Fix 9: Skip Liners and Clean Around It

The AAFP and ISFM advise against litter box liners, alongside scented litters and deodorizers. A bare box that you wash with hot water and mild soap at each full change is the simpler route to a fresh box.

Clean the floor around the box too. Stray litter and the occasional miss near the edge add to the smell. A washable litter mat under the box catches most of it.

When the Smell Means a Vet Visit

Sometimes the smell isn’t about the box. Mountain Veterinary Clinic notes that dehydration, urinary tract infections, diet, kidney disease or diabetes can all change how a cat’s urine smells. It describes infection as causing a foul, pungent odor, and kidney disease or diabetes as linked to a sweet or chemical-like smell.

If your cat’s urine smells different from usual, or the smell persists despite a clean box, book a vet visit. Call sooner if you also see changes in how often your cat pees or any accidents outside the box.

The Bottom Line on Litter Box Smell

Frequently Asked Questions

Why does a clean litter box still smell?

Bacteria stay in the litter that’s left after scooping and keep turning urine into ammonia. A scratched plastic box can also hold bacteria that washing doesn’t reach. Do a full change and wash with hot water and mild soap, and replace the box if it’s old and scratched.

What gets rid of litter box smell fast?

Scoop immediately, then do a full change: bin the old litter, wash the box with hot water and mild soap, dry it, and refill with about two inches of unscented clumping litter. Open a window for fresh air. Skip air fresheners, which only cover the smell.

Does baking soda help with litter box smell?

A little. Baking soda neutralizes some odor, but its effect in our tests was modest. Activated carbon traps ammonia more effectively, and research summarized by Litter-Robot found cats preferred carbon to baking soda. Neither replaces daily scooping.

How often should I clean the box?

Scoop at least once a day, and twice if you can. Do a full change and wash the box every one to four weeks, as the AAFP and ISFM advise, or sooner if it still smells after scooping. Cats sharing one box shorten that schedule.

Can a smelly box mean a sick cat?

Sometimes. If the box is clean but the urine itself smells unusual, a vet clinic notes that dehydration, infection, diet, kidney disease or diabetes can be the cause. See your vet if the smell changes suddenly or persists, especially with any change in toilet habits.