What this calculator does
A rough guide for a dog is about 50 ml of water per kilogram of body weight a day, so a 20 kg dog needs somewhere around a litre. Low activity pulls that towards 40 ml per kg and hot weather or hard work pushes it towards 60 or beyond.
What the figure is actually useful for is spotting change. Dogs regulate their own intake well, and the absolute number matters far less than whether it has shifted. A sustained increase in drinking is one of the more common early signs of kidney disease, diabetes and several other conditions, and it is worth a vet visit rather than a wait.
The formula
Body weight in kilograms is multiplied by the millilitres per kilogram for the activity level chosen. The result is converted to litres and US cups. The guideline is a broad one: food type alone shifts intake substantially, since wet food carries a great deal of water that dry food does not.
| Term | Meaning |
|---|---|
| ml per kg | The guideline rate, roughly 40 for a low-activity dog and 60 in heat or hard work. |
| Total intake | Water from all sources, including what is in food. Dogs on wet food drink noticeably less. |
| Polydipsia | The clinical term for excessive drinking, generally taken as sustained intake above about 100 ml per kg a day. |
The inputs explained
| Field | What to enter |
|---|---|
| Body weight (kg) | Body weight in kilograms. |
| Activity level | Activity and conditions. Heat, exercise and lactation all raise requirements well above the resting figure. |
When to use it
Checking whether drinking has changed
The useful comparison is against the same dog last month, not against a table. A clear and sustained rise is worth a vet visit.
Making sure enough water is available
On a hot day or a long walk, knowing roughly what a dog gets through helps with how much to carry.
Switching between wet and dry food
A dog moving from wet to dry food will drink considerably more, and that increase is expected rather than a warning sign.
Worked examples
Every figure in the tables below is produced by this page’s own calculator at build time, so the numbers and the tool always agree. Select any row to load that scenario.
How much water does a dog need per day?
A range of body weights at the regular-activity guideline.
| Body weight | Daily water needed | In litres | In US cups |
|---|---|---|---|
| 5 kg | 250 ml | 0.25 L | 1.1 cups |
| 10 kg | 500 ml | 0.50 L | 2.1 cups |
| 20 kg | 1,000 ml | 1.00 L | 4.2 cups |
| 30 kg | 1,500 ml | 1.50 L | 6.3 cups |
| 45 kg | 2,250 ml | 2.25 L | 9.5 cups |
Questions
How much water should a dog drink a day?
Roughly 50 ml per kilogram of body weight, so about a litre for a 20 kg dog. The range runs from around 40 ml per kg for an inactive dog to 60 or more in heat or with hard exercise. Individual dogs vary and self-regulate well when water is freely available.
My dog is drinking much more than this. Should I worry?
A sustained increase is worth a vet appointment rather than a wait. Increased thirst is an early sign of kidney disease, diabetes, Cushing syndrome and several other conditions, and it is usually noticed before anything else. A one-off hot day is a different matter.
Does wet food count towards the total?
Yes, and substantially. Wet food is roughly three quarters water, so a dog eating it drinks noticeably less from the bowl while getting the same total. Comparing a wet-fed dog against this guideline will make it look like it is drinking too little.
What if my dog barely drinks at all?
Reduced intake matters as much as increased intake and is harder to notice. If it persists beyond a day, or comes with lethargy, vomiting or a dry mouth and gums, contact a vet. Dehydration develops faster in small dogs and in hot weather.
For daily calories rather than water, see the dog and cat calorie calculator. For how much food to weigh out, see the dog daily food calculator.