How much food a dog needs varies depending on the dog's size. For instance, if the dog weighs 5 pounds, it should eat slightly more than a half cup of dry food daily, according to Nature's Logic. The activity level of a dog also needs taken into consideration for feeding amounts.
A small dog that weighs less than 10 pounds and is moderately active should be fed around a 3/4 cup of dry food or 5.7 ounces of wet food per day. Dogs that are between 25 and 40 pounds need around 1.4 cups of dry food or 14.6 ounces of wet food per day. Larger dogs require slightly larger amounts, such as 4 cups of dry food. Dogs should be fed two to three times per day.