Just as people vary our canine companions have individualized nutritional requirements.  Estimated energy requirements are based on the weight of each animal as well as the average amount of energy various tasks require.  The chart below illustrates the recommended caloric intake each day for dogs of different weights with a basic Resting Energy Requirement (RER).  RER represents the energy requirement for a normal animal at rest in a thermoneutral environment at a specific body weight.  However the suggested amount of calories consumed daily will vary dependent on the age of the dog physical stature and work load.

For young pups under the age of 4 months multiply the Resting Energy Requirement (RER) x 3.
For pups 4 months and older multiply the RER x 2

For maintenance of adult dogs alter the RER as follows:
normal neutered adult:  multiply RER x 1.6
intact adult:  multiply RER x 1.8
obese-prone:  multiply RER x 1.4
for weight loss:  RER remains as listed

For working dogs the RER should be adjusted to fit the amount of physical activity used:
light work:  multiply RER x 2
moderate work:  multiply RER x 3
heavy work:  multiply RER x 4

For example if your dog was a 85 lb. 3 year old unspayed female who consistently had a heavy work load you would compute the daily energy requirement as follows:
1065 (base RER) x 1.8 (intact adult) = 1917 x 4 (heavy work) = 7688 calories needed/daily.