How much water should my dog or cat drink?
A daily requirement for either species, worked two independent ways — and, more usefully, the published threshold above which drinking is a symptom rather than a habit.
Daily water requirement
—
ml per day
- Published range
- —
- Per kg
- —
Your measurement (drinking only)
—
ml per kg per day
- Polydipsia threshold
- —
Two sources, two routes, one answer
Water requirements can be worked out per kilogram of body weight or from metabolic energy, and the two
published routes land in the same place. The University of Guelph, in a page reviewed by
a board-certified veterinary nutritionist, gives a range: 60–80 ml/kg for
dogs and 40–60 ml/kg for cats. A clinical article on
dvm360 gives a formula instead: 140 × kg0.75 for dogs and
80 × kg0.75 for cats.
At a 20 kg dog the formula gives about 1,324 ml and the range gives 1,200–1,600 ml. At a 4 kg cat, 226 ml against 160–240 ml. They agree — but only between about 9.5–29.5 kg for dogs and 3.5–16 kg for cats, which covers most pets but not the whole chart.
Outside that range they diverge, and the reason is worth knowing. The formula scales as kg0.75, so it predicts a larger requirement per kilogram for small animals; the published range is linear and does not. At 1 kg the formula gives 140 ml/kg against a stated range of 60–80. Both are published figures, and neither is wrong — they are answering slightly different questions, and a tool that showed you one without the other would hide that.
What you measure at the bowl is not total water
Water requirements describe total water from all sources, food included. What you measure at the bowl is drinking water only, so it will normally sit below the requirement without anything being wrong.
This is why the polydipsia threshold is the number worth watching. It describes drinking, which is what you can actually measure, and it is a defined finding rather than a range. The requirement figures above describe total water, most of which may arrive in the food.
When drinking more is a symptom
Sustained intake above 90 ml/kg/day in dogs or 45 ml/kg/day in cats meets the published definition of polydipsia. The word describes the finding, not the cause. Diabetes mellitus, chronic kidney disease, Cushing's disease, hypercalcaemia, pyometra and a number of drugs all produce it, and several are treatable if caught early.
Do not diagnose from one day. Hot weather, exercise, a change of food from dry to wet, a salty treat and simple boredom all raise intake. The clinical threshold describes a persistent pattern, which is why the note above asks you to measure over more than 24 hours before drawing a conclusion — and why the answer to a high reading is a vet visit, not a diagnosis from this page.
Water drunk is not the whole story
What you see in the bowl understates total water intake, because food contributes a great deal. Dry food is around 10% moisture, wet food more than 65%. A cat eating only dry food may drink noticeably more than one eating wet food, and still be taking in less water overall.
That matters most for cats, who evolved as desert hunters and have a comparatively weak thirst drive. If a cat drinks very little, the practical fix is usually to add wet food rather than to try to make the cat drink.
Published daily water intake by weight
| Weight | Dog | Cat |
|---|---|---|
| 2 kg | 120–160 ml | 80–120 ml |
| 4 kg | 240–320 ml | 160–240 ml |
| 6 kg | 360–480 ml | 240–360 ml |
| 8 kg | 480–640 ml | 320–480 ml |
| 10 kg | 600–800 ml | — |
| 15 kg | 900–1200 ml | — |
| 20 kg | 1200–1600 ml | — |
| 25 kg | 1500–2000 ml | — |
| 30 kg | 1800–2400 ml | — |
| 35 kg | 2100–2800 ml | — |
| 40 kg | 2400–3200 ml | — |
| 45 kg | 2700–3600 ml | — |
| 50 kg | 3000–4000 ml | — |
The published table stops the cat column at 8 kg and the dog column at 50 kg. Blank cells are blank in the source, not omitted here.
Frequently asked questions
How much water should a dog drink per day?
Roughly 60 to 80 ml per kg of body weight, or 140 × (weight in kg)^0.75 millilitres. A 20 kg dog therefore lands around 1,200 to 1,600 ml. Both routes are published by different sources and agree, which is why this page shows both.
How much water should a cat drink per day?
Roughly 40 to 60 ml per kg, or 80 × (weight in kg)^0.75 millilitres. A 4 kg cat lands around 160 to 240 ml. Cats evolved to get much of their water from prey, so many drink less than they need, especially on dry food.
How much water is too much for a dog?
Sustained intake above about 90 ml/kg/day in dogs, or 45 ml/kg/day in cats, is the published definition of polydipsia. For a 20 kg dog that is roughly 1.8 litres a day. It is a referral threshold rather than a diagnosis: many conditions cause it, and one hot day does not.
Is this veterinary advice?
No. It is an educational calculator on published figures. Measuring water intake accurately means measuring what you put down and what is left, over a full day, with no other water sources. If the number concerns you, take it to a veterinarian rather than acting on it.
Sources
- University of Guelph, Ontario Veterinary College — Beat the Heat: Your Guide to Pet Hydration. Reviewed by Adronie Verbrugghe, DVM, PhD, Dip ECVCN. Source of the per-kilogram ranges and the weight table. uoguelph.ca
- dvm360 — The ins and outs of polyuria and polydipsia in veterinary practice. Source of the per-species formula and the polydipsia thresholds. dvm360.com
How these sources were chosen, and what this site does not do: about & methodology. Feeding questions are covered by the dog calorie calculator and the cat feeding calculator.
Educational use only. Not a veterinary service, and it cannot examine your pet or know about other water sources. A persistent change in drinking or urination is a reason to see a veterinarian, not a reason to adjust anything yourself.