How much should pets drink?
Water makes up about 60 to 70% of a dog’s or cat’s body weight, and losing just 10% of body water can be dangerous. Daily needs depend mainly on body weight, then on activity, temperature and diet. This calculator estimates total needs, subtracts the water already in the food and gives the amount your pet should drink from the bowl.
The rule of thumb
- Dogs: about 50 to 60 mL per kilogram per day, roughly 1 ounce per pound.
- Cats: about 40 to 60 mL per kilogram per day, roughly 1 cup for a 10-pound cat.
The calculator uses 55 mL/kg for dogs and 50 mL/kg for cats, raised by 25% for active pets or warm weather and 50% for very active pets or heat.
Food counts too
Dry kibble contains about 10% water, while canned or pouch food is about 75 to 80% water and raw or home-cooked diets around 70%. A cat eating 6 ounces of wet food a day gets about 4½ ounces of water from it, which may cover most of its needs. That is why cats on wet food often seem to drink very little.
Worked example
A 30-pound dog (13.6 kg) with normal activity needs about 13.6 × 55 = 750 mL, or 25 fluid ounces, a day. If it eats 5½ ounces (156 g) of kibble, the food provides only about 16 mL, so it should drink about 730 mL, just over 3 cups. On a hot summer day, plan for half as much again.
Signs of drinking too much
Drinking more than about 100 mL per kilogram per day is called polydipsia. For the 30-pound dog, that is more than about 1.4 liters (46 ounces) a day. Common causes include:
- diabetes mellitus
- chronic kidney disease, especially in older cats
- Cushing’s disease in dogs, or an overactive thyroid in cats
- uterine infection (pyometra) in unspayed females
- some medications, such as steroids or diuretics
To measure intake, fill the bowl with a known amount each morning and measure what is left 24 hours later, accounting for evaporation and other water sources.
Signs of drinking too little
Dry, sticky gums, sunken eyes, lethargy and skin that stays tented when gently pinched suggest dehydration. Cats are particularly prone to urinary crystals and bladder problems when they drink too little. Offer wet food, several bowls, a pet fountain and fresh water every day.