Formula

As a general guideline, the daily water requirement of dogs and cats, expressed in ml/day, is roughly equivalent to the daily energy requirement (DER) in kcal/day (for dogs 1.6 x resting energy requirement [RER], for cats 1.2 x RER).

dogs requirement of water (ml/day) = (70 (body weight in kg)^0.75) x 1.6

Example

What is the daily water requirement of a 24 pound dog?

24 pounds converted to kilograms (24 divided by 2.2) is 10.91 kg

(70(10.91)^0.75) x 1.6 =

70(6) x 1.6 =

420 x 1.6 = 672 ml

OR

672 ml = (672 / 236.6) 2.84 cups or 2 cups & (0.84 x 8) 6.72 ounces

General Rule

I hope you found this page interesting and informational.  Although, a dog's water requirements are dynamic and very day to day.  ALWAYS PROVIDE YOUR DOG WITH CLEAN FRESH WATER unless your vet specifies otherwise.  Your dog is the best judge of how much water he needs.  Just keep that bowl full :)

Anecdote

This seems like a lot of water but don't forget your pet gets water from his food as well.  Dry foods contain around 8% water while canned food contains about 75% water.  I've search several sources on their recommendation with varying results.  Information by the Canadian government suggests dogs should have 80 ml of water /kg of body weight.  Veterinarian, Janet Tobiassen Crosby recommends dogs and cats should have 30 ml of water per pound of body weight which comes close to the formula on this page.

For Dogs at Risk - To Prevent Dehydration or Kidney Related Issues

 - Ensure multiple bowls of fresh water are available in prominent locations in the dog's environment.  This may mean providing several bowls outside as well as inside including each level of the home.

- Add small amounts of flavoring (e.g. salt-free bouillon) to make water more palatable especially in the winter months when getting fluids in can be more difficult but necessary with strenuous (sledding) exercise.

- Offer ice cubes as treats. This is also great for pups during teething periods or in the hot weather!

Reference

    Hand, M. S., Thatcher, C. D., Rimillard, R. L., & Roudebush, P. (Eds.). (2000) Small Animal Clinical Nutrition. (4th ed.). Marceline, MO: Walsworth.