At three months your baby should be sleeping an average of 15 hours between night time and day time sleep. Some babies sleep less, some more but pediatricians will tell you 15 hours is good for a 3 month old. Some sleep good at night, others sleep lots during the day, some do both which would make you very lucky ;-).
For formula, the rule of thumb is to offer him 2.5 ounces of formula per pound of body weight each day. So if he weighs 10 pounds, he should be getting 25 ounces of formula per day. That is just an estimation and some will eat more, some will eat less. You really should base it on your babies cues.
Babies typically eat every few hours (2-3), but again, sometimes more and some less. At 3 months they are the ruler of the roost and you should follow their cues to determine what they need. Good luck!
at 2:14 PM on Aug. 2, 2010