Ah, sleep. If you’re the parent of a newborn or older baby, chances are it seems like the days when you used to get a full-nights rest ar just a distant memory.

Although the majority of parents-to-be are under the impression that they have a good idea of what tired feels like, nothing quite prepares them for the sleepless nights they will face when their baby arrives.

As a night nanny and newborn specialist, the most popular questions I get from new parents are, “When can we expect to sleep again?” and “What’s normal for this age?” Below are some basic baby sleep guidelines by age and what to tell if your baby is on track for their age (remember, premature infants go by their due date adjusted age, not actual birth age for developmental reasons).

1-4 Weeks of Age : Newborns typically sleep about 15 to 18 hours a day, but only in short periods of two to four hours. Premature babies may sleep longer and colicky ones shorter.

Since newborns do not yet have an internal biological clock, or circadian rhythm, their sleep patterns are not related to the daylight and nighttime cycles. In fact, they tend not to have much of a pattern at all.

1-4 Months Old: 14 - 15 hours per day

By six weeks of age your baby is beginning to settle down a bit and you may notice more regular sleep patterns emerging. The longest periods of sleep run four to six hours and they tend to occur more regularly in the evening. It is during this stage that day-night confusion typically ends. Bedtimes should start to be between 6 to 8 p.m. by around 8 weeks, but you can still expect your child to get a couple times a night to feed. Naps are  irregular, but usually at least three or four a day are recommended and they should last anywhere between 30 minutes and two hours.

4-12 Months Old: 14 - 15 hours per day              

While up to 15 hours is ideal, most infants up to 11 months old get only about 12 hours sleep. Establishing healthy sleep habits is a primary goal during this period, as your baby is now much more social and his sleep patterns are more adult-like.

Babies typically have three naps but drop to two at around 6 months old, at which time (or earlier) they are physically capable of sleeping through the night. Establishing regular naps generally happens at the latter part of this time frame, as the baby's biological rhythms mature. The midmorning nap usually starts at 9 a.m. and lasts about an hour. The early afternoon nap starts from 12 to 2 p.m. and lasts an hour or two. And the late afternoon nap may start from 3 to 5 p.m. and is variable in duration. Bedtimes should continue to be early, around 6 to 7:30 p.m., and you can send them to bed even earlier bedtime if they have missed a nap or seem overtired.

1-3 Years Old: 12 - 14 hours per day

As your child moves past the first year toward 18-21 months of age they will likely lose their morning nap and nap only once a day, usually starting around 12 to 2 p.m., and lasting between one and three hours. While toddlers need up to 14 hours a day of sleep, they typically get only about 10. Many toddlers fight the afternoon nap time but need this sleep and you should continue to try and push for this rest time.

Most children from about 21 to 36 months of age still need one nap a day, which may range from one to three and a half hours long. They typically go to bed between 7 and 9 p.m. and wake up between 6 and 8 a.m.

So what to do if you baby falls far outside these guidelines? First, don’t panic, but make sure to see your pediatrician and share your child’s current sleep habits with him. Try using a sleep log to track the actual times and amounts your baby is sleeping (memories can get fuzzy when you’re tired and sleep charts can help fill in the gaps). And finally, hang in there- as one overtired mother told me, they eventually leave for college, right?