How Much Water Should a Dog or Cat Drink per Day?

A healthy dog needs roughly 50 to 60 ml of water per kilogram of body weight per day, which is about 0.75 to 1 fluid ounce per pound. Cats usually need a little less, about 40 to 60 ml per kg. That total includes the water in food, so a cat on wet food may drink very little from the bowl. Consistently drinking more than about 100 ml per kg (1.5 oz per lb) a day is a common definition of excessive thirst and is worth a vet visit.

The short answer

• Normal intake: about 50 to 60 ml per kg per day for dogs (roughly 0.75 to 1 fl oz per lb) and a little less for cats, about 40 to 60 ml per kg. Figures vary by source, diet, weather and activity.
• Rule of thumb: about one cup (8 fl oz, 240 ml) per day for every 8 to 10 lb of body weight.
• Wet food counts. Canned food is around 75 to 80 percent water, so pets on wet diets drink less from the bowl.
• Too much: more than about 100 ml per kg (1.5 fl oz per lb) per day is the widely used threshold for polydipsia, meaning excessive thirst.
• Common causes of increased thirst: diabetes, kidney disease, hyperthyroidism in cats, Cushing's disease in dogs, pyometra in unspayed females, and some medications.
• Measure before you worry. Two or three days of measured intake tells your vet far more than "she seems to drink a lot".

How much water should a dog drink per day?

A typical adult dog needs about 50 to 60 ml per kg per day, or around one fluid ounce per pound, a figure you will find repeated across veterinary references. A 20 kg (44 lb) dog therefore needs roughly 1 to 1.2 litres, a little over four to five cups, from all sources combined.

Dogs drink more when it is hot, after exercise, when nursing, and when they eat dry kibble. Puppies drink more per kilogram than adults. A normal dog's intake also varies from day to day, which is why a single unusual day means little and a pattern over several days means much more.

How much water should a cat drink per day?

Cats usually need a little less in total, roughly 40 to 60 ml per kg per day, and they get more of it from food and drink less from the bowl than dogs do. Cats evolved from desert-dwelling ancestors and have a weak thirst drive. A 4 kg (9 lb) cat needs about 160 to 240 ml a day in total, less than one cup.

A cat on a fully wet diet may take in most of that from food and barely touch the bowl. That is normal. A cat on dry food alone needs to drink most of it, so the same cat on kibble will visibly drink more. Some sources consider a cat consistently drinking more than about 45 to 50 ml per kg from the bowl worth checking, especially on wet food; the exact cut-off varies.

Water intake chart by body weight

The ranges below use 50 to 60 ml per kg for normal total daily intake, and 100 ml per kg as the threshold for excessive thirst. They are estimates for healthy adults in a temperate climate and include water from food.

To work it out for your own pet, multiply the weight in kilograms by 50 and by 60 for the normal range, and by 100 for the upper limit. In pounds, multiply by 0.75 and by 1 for fluid ounces.

Does wet or dry food change how much a pet drinks?

Yes, a lot. Dry food contains only about 10 percent water, while canned or pouch food is typically 75 to 80 percent water. A 156 g (5.5 oz) can of cat food supplies roughly 120 ml of water, which can be half or more of a small cat's daily need.

This matters in two ways:

1. A diet change can look like a health change. Moving a cat from wet to dry food will make it drink noticeably more from the bowl, and that is expected.
2. Bowl intake alone can mislead. When you tell your vet how much your pet drinks, also say what it eats, so they can estimate the total.

For cats with kidney disease or a history of urinary problems, vets often recommend wet food or water fountains precisely to raise total water intake.

How do you measure how much your pet drinks at home?

Measuring is simple and gives your vet real numbers to work with.

1. Use one water source. Pick up extra bowls for the test period, or measure each one.
2. Fill the bowl with a measured amount each morning using a measuring jug. Use more than your pet could drink in a day.
3. Set a control bowl with the same amount of water somewhere your pet cannot reach, to account for evaporation.
4. Next morning, measure what is left in both bowls. Water drunk equals the starting amount minus what is left, minus what evaporated from the control.
5. Repeat for two to three days and average the results. One day is not enough.
6. Divide by body weight in kilograms and compare with the table above.

If you have more than one pet, separate them during the test if you can, or measure household intake and tell your vet how many animals share the bowl. Water from toilets, puddles, garden ponds or dripping taps will not be counted, so block access where possible. Note how often your pet urinates too: increased thirst (polydipsia) and increased urination (polyuria) usually appear together.

Why is my dog or cat drinking more water than usual?

Some causes are harmless: heat, exercise, a switch to dry food, a salty treat, or a nursing mother. If none of those apply and the increase lasts more than a day or two, the Merck Veterinary Manual and most clinical references list these as the main medical causes:

• Diabetes mellitus. High blood glucose spills into the urine and pulls water with it. Weight loss despite a good appetite is typical. If your pet is already diabetic, rising thirst often means control is slipping; see our guide to tracking glucose and insulin in diabetic pets.
• Chronic kidney disease. Very common in older cats and also seen in dogs. Kidneys lose the ability to concentrate urine, so the pet drinks to keep up.
• Hyperthyroidism in cats. Usually cats over about 10 years; weight loss, a big appetite, restlessness and sometimes vomiting.
• Cushing's disease (hyperadrenocorticism) in dogs. Mostly middle-aged and older dogs; a pot belly, panting, thinning coat and a large appetite are common.
• Pyometra. A uterine infection in unspayed females, often a few weeks after a heat. Thirst, lethargy, vomiting and sometimes vaginal discharge. This is an emergency.
• Liver disease, urinary tract or kidney infections, and high blood calcium.
• Medications. Corticosteroids such as prednisolone, diuretics and some anti-seizure drugs commonly increase thirst. Ask your vet whether a new drug explains it before stopping anything.

Less common causes include diabetes insipidus and psychogenic drinking in dogs. Only testing can tell these apart, which is why a vet will usually ask for blood work and a urine sample.

When should you call the vet about increased thirst?

Book an appointment within a few days if:

• Measured intake is consistently above about 100 ml per kg per day
• Your pet is drinking and urinating more for more than a few days with no obvious reason
• You notice accidents in the house, a fuller litter box or larger clumps
• Thirst comes with weight loss, a change in appetite or a dull coat

Go the same day if increased thirst comes with:

• Vomiting, not eating or marked lethargy
• An unspayed female who has recently been in heat
• A diabetic pet that is also weak or vomiting
• Signs of pain, which can be subtle in dogs; see signs your dog is in pain

Drinking much less than usual also matters, especially in cats. A pet that stops drinking and eating, or shows dry gums and lethargy, needs a vet promptly. For a broader list of warning signs, see signs your cat is sick.

When you call, bring the numbers: measured intake per day, what your pet eats, current medications and body weight. A fresh urine sample in a clean container is often useful.

How can you track water intake in PetVitals?

In PetVitals you can log measured water intake and body weight as health records, and add symptoms such as increased urination with a date. The charts show whether intake is creeping up over weeks rather than just one hot day, and you can export a PDF report with those entries to hand to your vet. Daily reminders make it easier to measure at the same time each morning during a test period.

This article is for general information and does not replace a veterinarian. Water needs vary with diet, climate, age and health. If your pet's drinking has changed and you are not sure why, talk to your vet.

Knowing your pet's normal is the easiest way to spot a change early. PetVitals is available for iPhone and Android if you want to keep those numbers in one place.