The amount of food a puppy should eat depends on what breed the puppy is and what size the dog will be once it is fully grown. For the first six to eight weeks of a puppy's life, it should be allowed to nurse whenever it and the mother want.
Once puppies are eating solid food, small meals are easier to digest than large meals, so they should be fed small amounts three or four times a day. Specifically formulated puppy food will have extra calories and nutrients the dog needs. As a guideline, an owner should be able to feel the puppy's ribs, and see a distinct waist.