The working figure is about 50 millilitres per kilogram of body weight per day, counting every source. For a typical 4.5 kg cat that is somewhere near 225 ml, or a little under a cup.
That number is close to useless on its own, though, because most of it may never pass their lips.
Food does most of the work, or none of it
Wet food is roughly 70 to 80 percent water. Dry kibble is around 10 percent. That difference is enormous and it changes the whole picture.
- A cat on wet food gets a large share of its daily requirement from the food itself and may drink very little from a bowl. That is normal and not a problem.
- A cat on dry food has to make up almost the entire deficit by drinking. Studies of cats on dry diets consistently find they do not fully compensate, and end up running a mild ongoing shortfall.
So the honest version of the question is not "how much should my cat drink" but "how much water is my cat taking in altogether, and is the food covering it?"
What that looks like in a bowl
For the same 4.5 kg cat:
- Entirely wet food: perhaps 30 to 60 ml of drinking a day. Some barely touch the bowl.
- Entirely dry food: 150 to 200 ml of drinking a day would be doing well. Many manage noticeably less.
- A mix: somewhere between, in proportion.
How to measure it without turning it into a project
Fill the bowl to a marked line with a measuring jug. Twenty-four hours later, pour what is left back into the jug. The difference is roughly what went in, minus a little evaporation. Do it across three ordinary days and average them, because a single day tells you nothing.
With more than one cat this does not work, and you are stuck watching behaviour instead.
Making the number go up
In rough order of effect:
- Add wet food, even one pouch a day alongside kibble. This is by far the biggest lever and it is not close.
- Give them moving water. Cats will drink from a running source when they ignore a still one.
- Add more bowls, in different rooms. Cats drink opportunistically, so the bowl they walk past is the bowl they use.
- Move water away from food. Many cats will not drink beside a feeding spot.
- Change it daily and use a wide, shallow vessel so whiskers are not touching the sides.
When drinking changes, pay attention
The absolute number matters less than a change in it. A cat that suddenly starts drinking much more than usual, or emptying the bowl, is worth a vet visit. Increased thirst is one of the more common early signs of kidney disease, diabetes and hyperthyroidism, and all three are far more manageable when caught early.
A sudden drop matters too, particularly alongside lethargy or a change in litter box habits.
This is general guidance and not veterinary advice. If your cat's drinking has changed noticeably in either direction, or you are worried about dehydration, speak to a vet rather than adjusting a bowl.