How much water should a dog drink a day?

A healthy adult dog drinks roughly 50 to 60 ml of water per kilogram of body weight per day. A 10 kg (22 lb) dog drinks about half a liter, a 20 kg (44 lb) dog about a liter, a 40 kg (88 lb) dog about two. The water intake calculator gives the range for your dog’s weight, and the threshold above it that is worth a call to the vet.

That is the short answer. The rest of this post is about why the range is wide, what legitimately pushes a dog outside it, and how to actually measure intake — because “she seems to be drinking more” is one of the most useful things an owner can bring to an appointment, if it comes with a number.

Where the figure comes from

Water requirement tracks energy requirement closely: as a rule of thumb, about one milliliter of water per kilocalorie of maintenance energy. The NRC’s Nutrient Requirements of Dogs and Cats treats water as a nutrient and frames it this way. A typical adult dog’s maintenance requirement, worked out with the calorie calculator, comes to something in the region of 50 to 60 kcal per kilogram for a mid-sized dog — hence 50 to 60 ml per kilogram.

The rule of thumb is deliberately loose. Small dogs need more energy per kilogram than large ones, so they also drink more per kilogram; a Chihuahua at 70 ml/kg and a Great Dane at 45 ml/kg are both normal.

What changes the number

Diet is the biggest factor. Dry kibble is about 10% water. Canned food is about 78% water. A dog eating 400 g of canned food a day has already taken in around 300 ml before it touches the bowl, so it may drink half of what an identical dog on kibble drinks. Both are normal. Raw diets sit closer to canned than to dry.

Heat and exercise. Dogs cool themselves by panting, which is evaporative, so a hot day or a hard run can raise the requirement by half again or more. That is transient: intake should fall back once the dog has recovered.

Life stage. Puppies drink more per kilogram than adults, in line with their higher energy requirement. Nursing female dogs drink dramatically more — milk is mostly water and they are producing a lot of it.

Medication. Corticosteroids (prednisone and relatives) and diuretics both increase thirst as an expected effect, not a warning sign. If your dog is on either, the range in the calculator will not apply as written.

The number that matters: 100 ml/kg

Sustained water intake above about 100 ml per kilogram per day is called polydipsia, and it is a clinical sign. For a 20 kg (44 lb) dog that is 2 liters a day. For a 10 kg (22 lb) dog, a liter.

One hot day above the line is not a concern. Three days running, in a dog that has not changed food and is not on medication, is. The common causes of polydipsia in dogs are kidney disease, diabetes mellitus, Cushing’s disease and — in an unspayed female dog — pyometra, a uterine infection that is a surgical emergency. In all of these, increased drinking is often the first sign the owner notices, sometimes weeks before anything else looks wrong. Older dogs are over-represented; if yours has crossed into the senior bracket by the senior age checker, a change in thirst is worth more attention, not less.

Do not restrict water to control drinking. If a dog is drinking to excess, it is almost always because it is losing water to excess, and restricting intake produces dehydration on top of whatever is driving it. Measure, and take the measurement to the vet.

How to measure it

The method is simple and takes three days:

1. Each morning, fill the bowl with a measured amount — use a measuring jug, not an estimate.
2. Top up during the day with measured amounts, and write each one down.
3. After 24 hours, measure what is left and subtract.
4. Repeat for three days and average the result.

If you have more than one dog, this only works if they can be separated, or if you can be confident which dog is drinking. A camera pointed at the bowl settles it.

Arriving at the vet with “she is drinking about 2.4 liters a day, measured over three days, on dry food” is a diagnostic starting point. “She seems thirsty” is not. The measurement also gives a baseline: a 20 kg (44 lb) dog whose intake later climbs from 1 liter to 1.8 has changed by 80% even though 1.8 is still below the 2 liter polydipsia line for its weight.

The other direction

A dog that barely drinks is usually not a problem, especially on wet or raw food, where most of the requirement arrives in the bowl. A dog that suddenly stops drinking, or drinks far less alongside lethargy, vomiting or diarrhea, does need checking — vomiting and diarrhea both lose fluid on top of the reduced intake.

Water should always be available. Free access, changed daily, in a bowl that is washed rather than topped up. Everything above is about reading what the dog does with that access, not about rationing it.

Tools in this post

• Dog Daily Water Intake Calculator →

  Dog water intake calculator: how much water your dog should drink each day, and the intake that suggests excessive thirst worth a vet visit.

• Dog Calorie Calculator →

  Calculate how many calories your dog needs per day from body weight, life stage and activity level, using the standard RER and MER veterinary formulas.

• Senior Dog Age Calculator →

  Senior dog age calculator: find out whether your dog counts as senior yet, since the threshold shifts by several years between small and giant breeds.

Sources

• National Research Council. Nutrient Requirements of Dogs and Cats. Washington, DC: National Academies Press; 2006.
• WSAVA Global Nutrition Committee. Global Nutrition Guidelines and toolkit.