As a concerned cat guardian I rely on my cat to decide how much water he needs to drink in a day to sustain him provided water is unlimited which it always is for the well cared for domestic cat. What I am saying is that I have to rely on someone else more expert than me to tell me how to determine an average adult cat’s daily water requirement. Linda P. Case the author of The Cat It’s Behavior, Nutrition & Health writes that a domestic cat needs an amount “roughly equal to the number of kilocalories of energy consumed per day”. Thankfully, she explains what that means.
Working out daily water needs
A ten pound cat (an average weight at 4.5 kilograms) has a daily energy requirement of 360 kcal per day. They require about 360 ml (millilitres) of water per day. This is about 1.5 cups of water which seems an awful to me (see below). But if a cat is on wet cat food they will obtain most if not all of the water they need from their food which is 80% water. Domestic cats are bad drinkers because of their inheritance from wild cats living in semi-desert regions.
My research indicates that the kcal requirement of 360 above applies to outdoor cats. Indoor cats require 20 kcal per pound of weight. This is 200 kcal for a ten pound cat. These cats need 200 ml of water daily. Another source states that “an active adult cat will need about 30 to 35 calories per pound of body weight per day, and some will do well with about 25 calories”1. This information points to around 300 ml of water daily for the average cat or less.
Another veterinary source2 states that a ten pound cats needs 7-9 ounces of water per day. Nine ounces of water is 255 ml of water. My conclusion therefore in taking on board these various sources is that ten pound adult cats need about 200-350 ml of water per day depending on the their activity levels and what advice you wish to believe. This is between one cup + 2 Tbsp, and 1.5 cups of water.
Dry cat food changes things
I recently discussed dry cat food and how it predisposes cats to urinary tract problems. Here is the problem surfacing again. Cats who are fed a dry kibble diet usually consume less water than do cats on a canned food diet (because they don’t fully compensate for the loss of water in their food). Linda P. Case says that domestic cats regulate their water intact. Yes and no. They are fooled by the unnaturalness of dry kibble. They don’t regulate their water intact correctly under these circumstances by drinking more water. They become slightly dehydrated.
1. Cat Owner’s Home Veterinary Handbook.
2. Online vet website.
P.S. I have written on this topic before. I only realised it after I’d finished. This may be the better version.