In a perfect world a baby should eat 2 ounces per pound of body weight in a day...example: 10 pounds= 20 ounces. For some it's more, for some it's less depending on they're metabolism. To be honest I don't pay much attention to that. If they cry I give them a bottle. If they're in the habit of drinking 4 ounces or 5 ounces then I make a 6 ounce bottle so I can be sure there's enough...then I let them have how much of that bottle they want. If they bat the bottle of their mouth, turn their head from it or just stop sucking, then they're done. You'll probably waste more that way, but atleast you know she's had her fill. She's not going to take more than she can handle and she's not going to take less than she needs. As a result I've always had healthy happy babies. As long as she's fed and clean she's happy. My second child was taking 4 to 5 ounces a feeding by his second day of life (back then they kept you in the hospital 3 days) the hospital put him on cereal that second day to slow him down on the formula...and he never got fat, he just burned it off really fast. Don't try to decide how much she's going to eat, let her guide you.