What bedtime for a peaceful wake-up?

How the bedtime is calculated

The calculator starts from the wake-up time and works back through the night. It subtracts the amount of sleep recommended for the age, then fifteen minutes to fall asleep. Because the recommendation is a range, it gives two times: the earlier one matches the top of the range, the later one the bottom. The time shown is lights out, not the start of the bedtime routine.

The durations come from the National Sleep Foundation. A panel of eighteen experts settled on 10 to 13 hours for ages 3-5, 9 to 11 hours for ages 6-13 and 8 to 10 hours for ages 14-17 (Hirshkowitz et al., 2015). The American Academy of Sleep Medicine reached very similar ranges in 2016. These are the same figures as in our guide to sleep needs by age.

An example: a 7-year-old wakes up at 7:00. They need 9 to 11 hours of sleep, which is 9 h 15 to 11 h 15 once you add the time to fall asleep. The calculator answers: bedtime between 19:45 and 21:45.

The tool does not cover children under 3. At that age, naps carry a large share of the total, and treating the recommended 11 to 14 hours as a single night would give bedtimes far too early. For toddlers, start from the guide on naps.

Why a 90-minute sleep-cycle calculator does not suit a child

Most bedtime calculators you find online are built for adults. They count 90-minute cycles and suggest going to bed five or six cycles before the wake-up time, which means 7.5 to 9 hours of sleep. For a child, that logic fails for two reasons.

First, the cycle is not the same length. In a baby it lasts about 50 minutes, against 90 in an adult, and the adult sleep structure only settles in around age 5. Cutting a child's night into 90-minute blocks applies a rule that is not yet theirs.

Second, the total need is higher. Five 90-minute cycles make 7.5 hours, less than the range for any child under 14. Six cycles (9 hours) only reach the bottom of the range for ages 6-13. A child put to bed by an adult's calculation falls asleep too late and builds up a sleep debt that the tool never flags.

This calculator works differently. It does not try to wake you at the end of a cycle; it aims for a total duration suited to the age, for a wake-up time that school has already set.

Recommended bedtimes by age and wake-up time

This table applies the tool's calculation to three common wake-up times. Each cell gives the range: the earliest time (top of the recommendation), then the latest (bottom of the recommendation), with fifteen minutes to fall asleep included.

The range is wide, up to three hours, because need varies from one child to another. Start in the middle and adjust: a child who has to be shaken awake in the morning, or who falls apart in the late afternoon, needs an earlier bedtime. The extreme times apply to a child who needs the top or the bottom of their range. Between 3 and 5, the recommendation includes the nap: subtract it from the night. A 90-minute nap pushes bedtime back by as much, and the times before 6 pm only apply to a child who needs the top of their range without a nap.

How to stick to the bedtime

Fix the wake-up time first, not the bedtime. It is the anchor everything else is worked out from, and it should barely move, weekends included. A two- or three-hour lie-in on Sunday often points to a bedtime that is too late during the week.

Move bedtime earlier in small steps, ten minutes every two or three days, rather than all at once. Falling asleep keeps pace and you do not add an evening battle to a sleep shortfall. For the daylight-saving change, the guide on the clock change covers the method.

Count the routine as part of your evening. If the calculation says 19:45, the bath, tooth-brushing and story start earlier. A routine kept up regularly is associated with better sleep in children under six (Mindell et al., 2015): see the guide on the bedtime routine.

Turn screens off well before lights out, as the guide on screens before bed explains. If your child refuses to go to bed at the calculated time, bedtime refusal offers some leads. For a teenager, whose body clock shifts later, read teenage sleep instead.

The result is a guideline. If your child sleeps below their range for weeks with no sign of daytime tiredness, their real need may simply be lower. If you stay unsure, talk to your pediatrician.