How to use the cat water intake calculator
- Enter your cat’s weight.
- Enter how much wet food it eats in a day and the moisture % on the label. Enter 0 for a dry-food-only cat.
- To check its drinking, measure the bowl for 24 hours: put in a known amount, top up with measured amounts and measure what is left.
- Read the total daily need, how much the food supplies and how much should come from the bowl.
The formula
Daily water need = about 50 ml per kg of body weight, counting water from food and bowl together (Royal Canin Academy; Cornell Feline Health Center gives about 4 oz per 5 lb of lean body weight, which is nearly the same).
Water from wet food = grams of food × moisture % ÷ 100, since 1 g of water is about 1 ml.
Too much = more than 100 ml per kg per day, the usual definition of polydipsia (UK veterinary referral fact sheet on polydipsia in dogs and cats).
Tips
- Measure all bowls. Include every water bowl and fountain in the house when you check 24-hour drinking.
- Dry food means more drinking. Dry food has little moisture, so a dry-fed cat gets nearly all of its water from the bowl.
- Bring numbers to the vet. A measured amount is far more useful than “drinking a lot”.
- Feeding amounts: see the cat food calculator.
Sources
- Royal Canin Academy (veterinary education site): typical recommendation of about 50 ml/kg/day for cats.
- Cornell Feline Health Center: about 4 oz of water per 5 lb of lean body weight a day, including water in food.
- UK veterinary referral fact sheet: Polydipsia in Dogs and Cats (vetspecialists.co.uk): increased thirst defined as over 100 ml/kg/day.
Frequently asked questions
How much water should a cat drink a day?
About 50 ml per kg of body weight a day in total, a figure cited by Royal Canin’s vet academy; Cornell’s Feline Health Center gives a similar figure of about 4 oz per 5 lb of lean body weight. For a 10 lb (4.5 kg) cat that is about 230 ml, or a little under 8 fl oz, from food and bowl together.
How much water does wet food give a cat?
Most of it. Wet food labels list a moisture percentage, and one gram of that water is about one millilitre. A 5.5 oz (156 g) can at 78% moisture holds about 122 ml of water, which is more than half of a 10 lb cat’s daily need.
Is it normal for my cat to drink very little?
Often yes, especially if it eats wet food. Cats evolved to get much of their water from prey. A cat on dry food should be drinking noticeably more from the bowl. If your cat seems lethargic, stops eating or passes little urine, call your vet.
How much water is too much for a cat?
Drinking more than about 100 ml per kg a day is the usual definition of increased thirst (polydipsia). In cats it can be a sign of kidney disease, diabetes or an overactive thyroid, so book a vet visit, especially if your cat is also urinating more or losing weight.
How can I get my cat to drink more water?
Feed some wet food, keep bowls clean and away from the litter box and food, try a wide shallow bowl or a water fountain, and offer water in more than one room. Ask your vet if your cat has a urinary or kidney problem.