Mix the new litter into the old over a week. Start at a quarter, step up every two days, and keep the old bag for a fortnight after you finish. Most cats never notice. The ones that do will tell you on day three, and the fix is to slow down, not to push on.
Mix the two litters together in the box rather than layering one on top of the other. Layers let your cat scrape down to the old stuff and learn that the new stuff is avoidable.
| When | In the box | What to watch |
|---|---|---|
| Days 1 to 2 | A quarter new, three quarters old | Nothing much should change. If it does, you have a fussy cat and the whole plan needs to run at half speed. |
| Days 3 to 4 | Half and half | This is where texture becomes obvious underfoot. Watch for shaking paws on the way out. |
| Days 5 to 6 | Three quarters new, a quarter old | Digging should still look normal. Short, hurried visits are a warning. |
| Day 7 | All new | Keep the old bag for another fortnight in case you need to go back. |
Cornell Feline Health Center lists a sudden brand change as one of the reasons a cat starts going outside the box, and says that if you must switch, do it gradually by adding small amounts of new litter to the old. A week of mixing is cheap insurance against a habit that can take months to break.
Buy the small bag of the new litter first. If your cat rejects it, you are out the price of one small bag instead of a warehouse pallet.
Keep enough of the old litter to refill one whole box. Going back on the same day a problem starts is what stops a one-off accident becoming a habit. If you are moving towards a fine-grained unscented clay, two of the strongest performers in our drop test are Dr. Elsey's Ultra and Boxiecat Premium.
The biggest texture jump there is. Fine grit to hard cylinders is a different floor under the paws, and pellets do not cover the way clay does.
What to do: Run the mix over two weeks rather than one, and put a second box with the old litter next to it so refusing is not the only option.
This one is usually easy. Cats mostly prefer unscented, so you are moving towards what they want, not away from it.
What to do: A straight swap is often fine. Mix over three or four days if your cat is generally cautious.
The hardest one to sell. A perfume the cat dislikes turns the box into somewhere to avoid, and you cannot negotiate with a nose.
What to do: Think again. If you are chasing smell control, changing how often you scoop moves the needle further than a fragrance does.
A week for most cats: start at a quarter new litter, and step up every two days until the box is all new. Cornell puts it plainly, if you must switch brands, do so gradually, adding small amounts of new litter to the old.
Plenty of cats accept it. The problem is what happens if yours does not, because a box refusal takes far longer to undo than a week of mixing would have taken.
If you have the room, yes. One box with the old litter and one with the new lets your cat pick, and which box gets used tells you exactly how the switch is going.
Go back to the last mix that worked and hold there for a few days before stepping up again. If a second attempt fails, the litter is wrong for that cat and no schedule fixes it.
A switch is only worth the week if the destination is right. Start from the tested picks rather than whatever is on the end of the aisle.
Activated carbon you add to the litter you already buy. We have used it in our own homes for years, and with dozens of friends and family. You can keep your existing base litter.
Read our Purrify guide to picking a litter for odor control.
The mixing schedule here follows the gradual-change advice published by Cornell's Feline Health Center, linked above. Product recommendations come from our own bought-and-tested reviews.