It's a funny thing about how much to feed. I think every dog is different.
Mickey eats 1/2 C of Wellness Small Breed or 1/2 C of Acana Grasslands (I rotate). Mickey is just the right weight. Not too skinny and not to fat. Little bit of fat on ribs and spine. He weighs only about 5.5 lbs.
Max on the other hand also eats 1/2 C of the foods and is fat. Can't feel his ribs or spine. Max weighs about 8 lbs but he is bigger than Mickey in bone size.
It makes no sense.
If Petco/Petsmart is where you get food, I have had great success with Wellness Small Breed.
I also rotate with Acana Grasslands and sometimes Prairie.
The boys love both