All babies are different, of course, but here are some general sleep guidelines, according to Kira Ryan, coauthor of The Dream Sleeper: A Three-Part Plan for Getting Your Baby to Love Sleep. As you'll see the suggested amount of sleep baby needs changes as he or she grows.
0 to 4 months
In that first month, baby may get up to 20 hours of sleep a day, waking only for short periods of time to feed. Over the next couple of months, baby will need about 15 to 18 hours of sleep a day—that's at least eight hours at night and seven during the day, spread over three naps.
4 to 6 months
Baby now needs slightly less shuteye—about 15 hours a day. Increase nighttime sleep to 11 to 12 hours, and reduce naps to three to four hours altogether, spread over three naps.
6 to 12 months
Baby needs about 14.5 hours of sleep a day, with about 11 to 12 during the night. The other two to three-and-a-half hours should come during two naps.
12 to 18 months
By now, baby will sleep about 14 hours a day—11 to 12 hours overnight, and one-and-a half to three hours during the day. Many babies switch from two naps to one during this time.
18 to 36 months
Nighttime sleep stays put at 11 to 12 hours. Most toddlers take one nap of about one-and-a-half to three hours.