How much should I feed my dog.

Question
I have a 1 1/2 years old male springer spaniel. I was wondering how much food I should be feeding him a day. He is very energetic and weighs about 50 lbs.

Answer
Maybe about 3 cups.  Your dog definitely should be narrower at the waist than the hips and chest. You should be able to easily feel the ribs, but not see them. Each dog is different.
Standard recommendations are a good place to start, but each dog must have its
food and exercise adjusted to its individual needs. Here is a link to a good
illustrated guide, http://www.longliveyourdog.com/twoplus/RateYourDog.aspx