Adult cats must drink the same water that is used to feed them. In veterinary medicine, cats need 44-66 ml of water per kilogram of body weight.
Canned food can contain up to 80% water, while dry food contains only 7% to 12% water. If you frequently feed your cat dry food, you'll need to provide even more water. 
If a cat weighs 5 kilograms, then the minimum daily water requirement for this cat is 220 milliliters.
This cat needs to eat 80 grams of dry food according to the feeding standard, which provides 8 milliliters of water. This means that this cat should drink an additional 212 milliliters of water.
This cat, according to the feeding standards, needs to eat 250 grams of canned food, which provides 200 milliliters of water. This means the cat only needs to drink an extra 20 milliliters.
How can I tell how much water my cat is drinking?You can check your cat's water intake daily by adding water from a bottle or a graduated cup.
If the indoor air is dry, this can lead to a significant amount of water evaporating. If multiple cats share the same bowl, this measurement method also requires averaging.
The best way to check if a cat is dehydrated is to test its skin elasticity. Lift the skin between the cat's shoulders and then release. If the skin takes more than a second to return to its original shape, the cat is showing signs of dehydration. Replenish fluids as soon as possible; severe cases require veterinary treatment.
