Dog & Cat Water Intake Calculator

Why thirst is worth measuring

Increased drinking, and the increased urination that goes with it, is an early sign of chronic kidney disease, diabetes, Cushing's disease, an overactive thyroid in cats, liver disease and uterine infection (pyometra) in unspayed females. Several of these are far easier to manage when caught early.

Owners usually notice a change in the water bowl before anything else — but a feeling that the bowl empties faster is hard for a vet to act on. A measured 24-hour figure, repeated over two or three days, is much more useful.

How to measure it properly

Fill the bowl with a measured amount first thing in the morning, using a measuring jug. Twenty-four hours later, measure what is left, and subtract. Account for any top-ups. If there are several pets, measure them separately or divide the total honestly.

Do it for two or three days, because intake varies with weather and exercise. Then enter the average above.

What changes normal intake

Hot weather, exercise, lactation and a dry-food diet all raise intake. Wet food lowers the amount drunk from the bowl, because a can of wet food is around three quarters water. Some medicines — steroids such as prednisolone, and some diuretics and anti-seizure drugs — raise thirst as a side effect.

Drinking too little matters too, especially in cats, which are prone to urinary problems when they are chronically under-hydrated. A water fountain, several bowls in different places, and wet food all help.

When to call the vet

Book a check if a measured intake is consistently over the excessive line, if thirst has clearly increased over weeks, or if increased drinking comes with weight loss, a change in appetite, accidents in the house or lethargy. The first test is usually a urine sample, which is cheap and informative.

Go the same day if an unspayed female is drinking heavily and seems unwell, especially a few weeks after a season, or if a pet that is not drinking at all is also vomiting.

Common questions

How much water should a dog drink a day?

About 50 to 60 ml per kilogram of body weight, or roughly an ounce per pound, including the water in food. A 40 lb dog typically takes in about 30 to 36 fluid ounces a day. Heat, exercise and dry food push it up.

How much water should a cat drink a day?

About 50 to 60 ml per kilogram including food moisture — around 200 to 250 ml in total for a 4 kg cat. A cat eating mostly wet food can get most of that from its food and may drink very little from a bowl.

Why is my dog drinking so much water?

Heat, exercise and a salty treat can all explain a short-term increase. A lasting increase — especially over 100 ml per kg a day — is a symptom worth investigating, most commonly for kidney disease, diabetes or Cushing's disease. Measure a 24-hour amount and see your vet.

Should I limit my dog's water?

No, not without veterinary advice. Restricting water in a dog that is drinking more because of an illness can make it dangerously dehydrated. Measure the intake and take the numbers to your vet instead.