What time should I go to sleep to wake up at 4:15 am?
To wake at 4:15 am on seven to nine hours
Be asleep between 7:15 pm and 9:15 pm
In bed between 7:00 pm and 9:00 pm, allowing 15 minutes to fall asleep
Seven hours is the floor the American Academy of Sleep Medicine's consensus statement sets for adults, so to wake at 4:15 am you want to be asleep by 9:15 pm at the latest. Nine hours puts the other end at 7:15 pm. Neither is a cliff edge; they bracket the range where most adults are getting enough.
By the hour
| Sleep | Asleep by | In bed by |
|---|---|---|
| 9 hours | 7:15 pm | 7:00 pm |
| 8.5 hours | 7:45 pm | 7:30 pm |
| 8 hours | 8:15 pm | 8:00 pm |
| 7.5 hours | 8:45 pm | 8:30 pm |
| 7 hours | 9:15 pm | 9:00 pm |
| 6.5 hours | 9:45 pm | 9:30 pm |
| 6 hours | 10:15 pm | 10:00 pm |
By sleep cycle
| Cycles | Time asleep | When to be asleep |
|---|---|---|
| 6 cycles | 9 hours | Asleep at 7:15 pm — in bed at 7:00 pm |
| 5 cycles | 7 hours 30 minutes | Asleep at 8:45 pm — in bed at 8:30 pm |
| 4 cycles | 6 hours | Asleep at 10:15 pm — in bed at 10:00 pm |
| 3 cycles | 4 hours 30 minutes | Asleep at 11:45 pm — in bed at 11:30 pm |
The cycle-aligned times below assume a flat 90-minute cycle, which is a population average rather than a fact about any one night. Real cycles run about 70 to 120 minutes, the first ones are shorter than the later ones, and their composition shifts from deep sleep towards REM as the night goes on. Treat the numbers as a target to aim at, not a schedule to hit. Total sleep matters considerably more than which minute you wake on.
What this actually assumes
- That you fall asleep in about 15 minutes. If you routinely lie awake for 45, every time above moves earlier by half an hour.
- That your cycles are 90 minutes. Across people they run 70 to 120, so by the fourth cycle the accumulated error can exceed an hour.
- That you sleep through. Brief awakenings are normal and get more frequent with age; they do not reset the cycle count but they do add to the time in bed.
- That the seven-hour floor applies to you. It is an adult figure. Teenagers need eight to ten and children more again.
How much sleep you need
| Age | Per day | Notes |
|---|---|---|
| Babies, 4 to 12 months | 12 to 16 hours, including naps | Counting naps. Sleep at this age is still spread across the day and the total is what matters, not the shape of it. |
| Toddlers, 1 to 2 years | 11 to 14 hours, including naps | Counting naps. Most children drop to a single daytime nap somewhere in this band. |
| Preschoolers, 3 to 5 years | 10 to 13 hours, including naps | Counting naps, which most children stop taking towards the end of this band. |
| Children, 6 to 12 years | 9 to 12 hours | Naps have usually stopped by now, so this is night sleep. |
| Teenagers, 13 to 18 years | 8 to 10 hours | Adolescent circadian timing shifts later by one to three hours at puberty, which is a biological change and not a behavioural one. A teenager who cannot fall asleep at 10 pm is usually not being difficult, and an early school start subtracts from the wrong end of the night. |
| Adults, 18 and over | 7 or more hours | The consensus statement gives a floor, not a range: seven or more hours on a regular basis. It does not endorse eight as a target, and it declines to state an upper bound, because regularly sleeping more than nine hours is associated with poor health outcomes without the direction of causation being established. |
Common questions
- What time should I go to bed to wake up at 4:15 am?
- Between 7:00 pm and 9:00 pm, which allows 15 minutes to fall asleep and gives you seven to nine hours.
- How many sleep cycles is that?
- Five ninety-minute cycles is 7 hours 30 minutes, putting sleep onset at 8:45 pm. Six is 9 hours, at 7:15 pm.
- Does waking at the end of a cycle actually help?
- It is a reasonable heuristic and not a schedule. Cycle length varies from about 70 to 120 minutes between people and across a single night, so a calculator cannot know where your boundaries fall. Total sleep matters more than the minute you wake on.
Related pages
- Waking at 4:45 am Asleep by 9:45 pm for seven hours
- Waking at 5:15 am Asleep by 10:15 pm for seven hours
- Going to bed at 9:00 pm The same question from the other end
- What a sleep cycle actually is And why the 90-minute figure is an average, not a clock
- When to stop drinking coffee Counted back from a 4:15 am wake-up
Sources
- Recommended Amount of Sleep for a Healthy Adult: A Joint Consensus Statement — Watson et al., Sleep 38(6) / Journal of Clinical Sleep Medicine, 2015
- Normal Human Sleep: An Overview — Carskadon & Dement, Principles and Practice of Sleep Medicine, 6th ed., 2017