Why Does My Cat’s Litter Box Still Smell (And How to Fix It)

We know the scenario: you just did a deep scrub of your cat’s litter box, waited patiently for it to dry, and refilled it with fresh litter, only to wonder: why does my cat’s litter box still smell? The truth is that there are a number of reasons why your cat’s litter box is still smelling, and it’s not a problem that is unique to you. Persistent litter box odor is one of the most common complaints among cat parents.

The good news is that understanding why your cat’s litter box is smelling can help you tackle the odor at its source. In this article, we’ll go over the causes of litter box odor. We’ll also provide you with practical litter box odor control tips to keep your home smelling fresh.

Here at Tuft & Paw, we are cat experts. The information in this article is based on consultation with veterinarians, online research, and our own experience as cat parents.

Why Does My Litter Box Smell So Bad?

There are a few reasons why litter box odors can linger. Understanding the causes of litter box smells can help you create an ideal litter box setup. 

• Ammonia breakdown: Bacteria turn urea from your cat’s urine into ammonia, which can lead to some pretty unpleasant scents. Heat and humidity speed up ammonia formation, so it’s best to keep your cat’s litter box in a cool, dry room.  Using highly absorbent cat litter also helps because it absorbs your cat’s urine, which can prevent ammonia from forming in the first place.

• Feces and sulfur compounds: Waste that has been left sitting for too long releases mercaptans and hydrogen sulfide, chemical compounds that cause odors that are anything but pleasant. Regularly scooping your cat’s litter is the best way to combat this. Using a litter that forms strong, solid clumps makes the cleaning process even easier.

• Porous plastic litter boxes: Scratches in porous plastic litter boxes can trap odors, meaning that your cat’s litter box still smells, no matter how much you clean it. We suggest using a litter box made of durable, non-stick, and odor-resistant plastic, such as Tuft & Paw’s Cubby Litter Box, or a stainless steel option.

• Wrong litter type: Not all litters are created equal. For managing odors, choose a cat litter that forms strong clumps. It should be unscented and have extra odor-neutralizing ingredients for the best results. Clumping clay, corn, and tofu litter tend to clump the best. Some cat owners also find success with silica gel crystals. While not clumping, silica gel is highly absorbent, which can help lock in odors. 

• Not using enough litter: The depth of litter in your cat’s litter box should be kept at 2-3 inches. This ensures there’s enough litter for it to absorb and clump properly (provided you are using a clumping litter). It also gives your cat enough litter to bury their waste.

• Diet and health factors: Dr. Amber Carter, a feline-exclusive veterinarian at Cat Care Clinic, notes the main health problem linked to litter box smell is urinary tract infections (UTIs). These are more common in older cats. While diet can also be an issue, she says that this is less of a worry for her if the cat is on an appropriate diet and is otherwise healthy. 

Why Your Litter Box Still Smells: Quick Guide

If the smell is…

• Sharp ammonia/urine smell: litter needs more frequent scooping or replacement, litter depth is too shallow, or your cat might be dehydrated.

• Fishy or unusually strong urine smell: possible urinary tract issue or infection; consider contacting your veterinarian, especially if the odor is new or accompanied by litter box behavior changes. 

• Rotten egg/sulfur smell: waste sitting too long or possible digestive issues.

• Musty plastic smell: scratched, aging, or odor-trapping litter box.

• The whole room smells: poor ventilation or litter box placement issue.

How to Eliminate Litter Box Odors

If you’re wondering how to eliminate litter box odor without constantly deep-cleaning, a consistent routine can make a major difference. Many of the most effective smelly litter box solutions focus on improving your cleaning habits, litter choice, and setup. 

Scoop at Least Once Daily

Scooping your cat’s litter box regularly is one of the most effective ways to manage litter box smells. Dr. Carter mentions that, ideally, cat owners should scoop their cat’s litter box any time there is waste so odors are quickly eliminated. Pair scooping your cat’s litter box with something you do daily, like brushing your teeth or making coffee. This makes it easier to add to your routine. 

Choose the Right Litter

The type of litter that you choose can really matter when it comes to controlling litter box smell. Clumping litters are often most effective because they form clumps around urine, preventing ammonia from forming. Litters that are low in dust and contain added odor control ingredients also perform well for odor control.  For more guidance in choosing litter, check out our post Best Cat Litter for Odor Control: Top 6 Picks and Expert Reviews.

Perform Regular Full-Box Cleanings

To fully clean your cat’s litter box, throw away any remaining litter into a trash bag and knot it. Then, clean the empty box and scoop using warm water and a mild, unscented soap. Allow the litter box to dry completely before filling it with 2-3 inches of litter. How often you need to perform regular full-box cleanings depends on the type of litter that you use. In general, clumping litter needs a full change every 2-4 weeks, whereas non-clumping litter needs to be fully changed every 5-10 days.

Ventilation and Box Placement

Box placement is often ignored when thinking about odor control, but it can really help odors dissipate to keep your home smelling fresh. It’s best to keep your cat’s litter box in a well-ventilated, open area and avoid closed spaces that trap heat, such as a bathroom or closet. In small spaces, placing your cat’s litter box near an open window or in a room with a fan can aid ventilation.

Add Odor Absorbers

Activated charcoal and baking soda are natural additives that can help with managing litter box odors without added fragrances. Activated charcoal works by chemically binding odor-causing molecules to its porous surface. You can either use a cat litter that contains activated charcoal (such as Tuft & Paw’s Really Great Cat Litter, OdorStop) or add an activated charcoal additive or filter to your cat’s litter box. 

Choose Your Litter Box Wisely

While covered litter boxes may help contain odors in the room temporarily, they can trap smells inside the box, creating an unpleasant experience for cats and reducing ventilation. Size also matters.  Heather Alvey, certified cat behavior consultant and owner of Felidae Behavior Consulting, says the larger the box you can offer your cat, the better! At a minimum, your box should be twice the width of your cat and 1.5 times the length from nose to bum so cats have enough room to move around comfortably in the box.

Consider Multiple Boxes

Whether you have multiple cats or not, having multiple boxes can prevent any single litter box from getting overused. The general rule is to have one more litter box than the number of cats that you have. For example, if you have two cats, you would have three litter boxes. If you have multiple cats, Alvey suggests placing litter boxes in various spots around the house. This helps prevent any one area from becoming a territorial hotspot.

How to Keep the Litter Box from Smelling: Long-Term Strategies 

If you’re regularly cleaning your cat’s litter box, have it well-placed, and are using a high-quality litter with added odor absorbers, but are still experiencing lingering unpleasant odors, it may be time to take a look at your cat’s diet and health.

Chronic dehydration can be common in cats and causes more concentrated urine, which can cause more intense ammonia odors. Adding wet cat food to your cat’s diet can help. You can also encourage them to drink more water. Try using a water fountain or adding tuna juice or chicken broth to their water. Wetting their kibble is another good option. Because cats can have trouble digesting legumes and carbs, consider trying a high-protein, low-carb wet food with few fillers. This can improve digestion and reduce smelly waste.

Several health issues can also result in smellier litter boxes, ranging from digestive issues and urinary tract infections to diabetes and kidney disease. Dr. Carter recommends seeing your vet whenever you notice a change in litter box odor that isn’t normal for your cat.

Odor Control Checklist: Daily Litter Box Odor Control Tips 

Daily

• Scoop waste and solid clumps 1-2 times per day

• Seal scooped waste in a knotted trash bag and dispose in a litter disposal system or an outdoor garbage can

• Top up litter to maintain a depth of 2-3 inches

• Ventilate the room by opening a window or running a fan

• Sweep up any loose litter around the litter box

Weekly

• Refresh or partially replace litter, depending on litter type

• Vacuum or sweep the area around the litter box

• Wipe surrounding floors and walls with a pet-safe cleaner

• Wash litter mats (if used) with mild soap and hot water

• Check the litter box placement to avoid any hot, humid spots

Monthly

• Dump all litter; wash box and scoop with mild soap or enzyme cleaner and hot water

• Inspect the empty litter box for any deep scratches

• Allow the litter box to dry fully before refilling it with 2-3 inches of litter

• Replace or clean the air purifier in the room

• Evaluate how well your cat’s litter is working and consider if it’s time to try something new

• Replace worn litter boxes and scoops as needed

Conclusion

Both the litter you use and your maintenance habits can play a role in how fresh your cat’s litter box is able to stay. Finding the right litter and the right routine for you and your cat can be a bit of trial and error, but many effective smelly litter box solutions come down to consistency and an appropriate setup. It’s often best to start with your litter box setup, including the box, the type of litter, and your cleaning routine. Small changes here can have big results in terms of odor control. And, as always, know that lingering litter box odors can be a sign of a health issue, so it’s never a bad idea to check in with your vet. 

Frequently Asked Questions

Why does my litter box smell so bad even after I’ve cleaned it?

This can happen because odors get trapped in the plastic, especially in deep scratches. Try a deep clean of your cat’s litter box and check for any scratches that indicate the litter box needs replacing. To prevent this in the future, consider switching to an odor-resistant plastic or stainless steel litter box.

What’s the best cat litter for odor control?

The best cat litter for odor control is highly absorbent, forms strong clumps, and contains added odor control ingredients. We recommend Tuft & Paw’s Really Great Cat Litter, OdorStop, which combines charcoal-infused tofu pellets, premium pea litter, and low-dust bentonite for a triple-action approach to managing odors. 

How often should I change my cat’s litter?

In general, clumping cat litter should be changed once every 2-4 weeks, while non-clumping litters need to be changed once every 5-10 days. The frequency can vary depending on the specific type of cat litter you’re using and how often your cat’s litter box is being used.

How do I keep my litter box from smelling between cleanings? 

Focusing on daily scooping, maintaining 2-3 inches of litter, using a high-quality clumping litter, and ensuring good ventilation around your cat’s litter box can help keep things fresh between cleanings. Some cat owners also find keeping an air purifier in the same room as their cat’s litter box helps reduce lingering odors.