How much litter should I put in the disposable litter box? This is a question we get quite allot of. The most straight forward answer is with our Cats Desire litter box, start with a 2-3 inch fill of a quality clumping clay litter. Other types work fine too, but clumping clay is still the workhorse of litter with it's ability to absorb in our opinion. This will give you a decent base to start with and figure out how much is needed through backfilling every time you take out. Some cats are vigorous diggers and require more litter to push around with their paws. Yes it is the pushing around of litter that's important to allot of Cats and another reason to use a good clumping clay litter since it has a heaviness that promotes the cat pushing the litter around while covering after using the box. So we advise customers to do just what we do. Start with a 20 pound bag of quality clumping clay litter, fill 2-3 inches, lean more toward 3, and monitor and then backfill as necessary. Until next time, Susan. Owner Cats Desire Litter Boxes.