Skibbit the advise I was given in the UK was :
One of the most confusing things about feeding your baby formula is trying to work out how much to feed him. And there's no single answer it depends on your baby's age, weight, and whether you're feeding him only formula, or using it in combination with breastmilk or solids. Here are a few pointers to help you decide how much your baby needs:
Multiply your baby's weight by 2.5 - 2.7 ounces of formula
If your baby isn't eating any solids (the recommended age for starting solids is six months), the general rule of thumb for formula amounts is 2.5 - 2.7 ounces (oz) per pound (lb) of body weight. So if your baby weighs 6lb, he should consume about 15 or 16oz of formula in a 24-hour period. If he weighs 10lb, he should have roughly 25 - 27oz in a 24-hour period.
http://www.babycentre.co.uk/refcap/9136.htmlThis is a guideline only, and I agree with Colenliam and Noelle every baby is different, and very worthwhile switching nipple/teat size.
hope this helps