Baby Sleep Calculator - Hours by Age and Bedtime Window

How much sleep a baby or child needs, and when bedtime falls

An 8-month-old who naps 3 hours and wakes at 7:00 AM should be asleep somewhere between 6:00 PM and 10:00 PM to land inside the 12 to 16 hours a day that sleep experts recommend at that age. This baby sleep calculator gets there from three inputs: age, the morning wake time and the hours of naps. Add last night's sleep and it also tells you whether the day's total is inside the range, below it or above it.

Four boxes on the form

Age - a number, with weeks, months or years next to it, from birth to 18 years. Six weeks, 8 months and 4 years all work.
Morning wake time - the usual time the day starts, as HH:MM.
Daytime naps - all naps added up, in hours; 0 once naps have stopped.
Night sleep - optional; hours actually asleep last night, for the check against the range.

Problem: the charts count the whole day, the bedtime is only the night

The expert ranges are hours per 24 hours. For babies, toddlers and preschoolers the American Academy of Sleep Medicine says so in plain words: "including naps". Count back from the wake-up time with the full 12 to 16 hours and the bedtime ignores the 3 hours already slept during the day, which puts it far too early. There is a second snag under 4 months: AASM gives no range at all, because sleep at that age varies too much to set one.

Solution: take the naps off first, then count back

Night sleep needed = recommended hours per day - naps. Asleep by = wake time - night sleep needed. For the 8-month-old: 12 to 16 hours minus 3 of naps leaves 9 to 13 hours of night, and 13 hours before 7:00 AM is 6:00 PM, 9 hours before is 10:00 PM. Under 4 months the calculator shows the National Sleep Foundation range of 14 to 17 hours and no bedtime, since, as NSF puts it, newborns rarely sleep through the night.

The result is the time to be asleep, not the time to go to bed. Settling down takes a while on top, and the calculator does not guess how long, because that varies from child to child.

Which range applies at which age

Two expert panels publish ranges, and they agree more than they differ. The calculator plans with the AASM range, which the American Academy of Pediatrics endorses, and shows NSF next to it; under 4 months only NSF has a number.

Age	AASM, hours per 24 h	NSF, hours per 24 h
0-3 months	no recommendation	14-17, naps included
4-11 months	12-16, naps included	12-15
1-2 years	11-14, naps included	11-14
3-5 years	10-13, naps included	10-13
6-12 years	9-12	9-11 (6-13 years)
13-18 years	8-10	8-10 (14-17 years)

Five households, five bedtime windows

Each row is a run of the calculator. The window is wide because it spans the whole recommended range, from its top to its bottom.

Child	Naps	Wakes	Night needed	Asleep by
8 months	3 h	7:00 AM	9-13 h	6:00-10:00 PM
18 months	2 h	6:30 AM	9-12 h	6:30-9:30 PM
4 years	1 h	7:00 AM	9-12 h	7:00-10:00 PM
9 years	0	6:45 AM	9-12 h	6:45-9:45 PM
15 years	0	6:00 AM	8-10 h	8:00-10:00 PM

Look at the 4-year-old and the 9-year-old. Different ages, different ranges, the same nine to twelve hours of night, because the younger child's hour of nap counts toward the day.

For babies under 1 year the result adds the American Academy of Pediatrics safe sleep points: on the back for every nap and at night, a firm, flat surface, no soft objects or loose bedding, a shared room for at least the first 6 months and no bed sharing.

What parents search for

How much should a baby sleep at 2 months?

The National Sleep Foundation gives 14 to 17 hours a day for 0 to 3 months, naps included. AASM sets no number before 4 months because sleep varies widely at that age, which is why the calculator shows no bedtime for a 2-month-old.

How much should a 4-month-old sleep?

From 4 months AASM recommends 12 to 16 hours per 24 hours including naps; NSF's range for 4 to 11 months is 12 to 15.

What if my child sleeps less or more than the range?

Enter last night's sleep and the result shows the gap in hours. AASM's own advice for parents who are concerned that a child sleeps too little or too much is to talk to their healthcare provider about a possible sleep problem.

Why does an earlier wake-up move the whole window?

Because the window is counted back from it. Wake at 6:30 AM instead of 7:00 AM and every bedtime in the window moves half an hour earlier, with the naps unchanged.

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