Working back from an 8:45 AM alarm
Each sleep cycle lasts roughly 90 minutes. Counting back from 8:45 AM in whole cycles, and allowing 15 minutes to drift off, gives these bedtimes:
- 11:30 PM (23:30): asleep by 11:45 PM for six cycles, or 9 hours.
- 1:00 AM (01:00): asleep by 1:15 AM for five cycles, or 7.5 hours.
- 2:30 AM (02:30): asleep by 2:45 AM for four cycles, or 6 hours.
Each of these lets your alarm go off close to the end of a cycle, when you are in lighter sleep and usually find it easier to get up.
Which 8:45 AM bedtime should you choose?
For most adults, 1:00 AM is the one to aim for. It gives 7.5 hours of sleep, above the 7-hour minimum recommended for adults aged 18 to 60.
11:30 PM gives 9 hours. It suits teenagers, who are recommended 8–10 hours, and anyone catching up after a run of short nights.
2:30 AM gives only 6 hours. It is better than waking mid-cycle after a slightly longer night, but keep it for the occasional late evening rather than a habit.
If you take more or less than 15 minutes to fall asleep
These bedtimes assume you take about 15 minutes to fall asleep. If you usually drop off faster or lie awake longer, use the row that matches you. The highlighted row matches the times at the top of this page.
| Fall asleep in | 9 h | 7.5 h | 6 h |
|---|---|---|---|
| 5 min | 11:40 PM23:40 | 1:10 AM01:10 | 2:40 AM02:40 |
| 10 min | 11:35 PM23:35 | 1:05 AM01:05 | 2:35 AM02:35 |
| 15 min | 11:30 PM23:30 | 1:00 AM01:00 | 2:30 AM02:30 |
| 20 min | 11:25 PM23:25 | 12:55 AM00:55 | 2:25 AM02:25 |
| 30 min | 11:15 PM23:15 | 12:45 AM00:45 | 2:15 AM02:15 |
Flexible days and days off
An 8:45 AM alarm is common on days off, during holidays, or for anyone with a flexible start. A 1:00 AM bedtime gives 7.5 hours, while 11:30 PM gives a full 9 hours. If you are going back to an earlier alarm later in the week, use the 11:30 PM option so the change is smaller.
Moving between very different sleep times from one day to the next is a bit like mild jet lag, so keeping your schedule within an hour or so helps.
Going back to an earlier alarm
If you have been waking at 8:45 AM on holiday and need to return to 6:30 or 7:00 AM, bring both times forward by about 15–30 minutes a day over the last few days. Getting daylight early each morning helps your body clock move with you.
More answers
- Bedtime for an 8:30 AM wake-upNearby answer
- Bedtime for a 9 AM wake-upNearby answer
- Bedtime for an 8:15 AM wake-upNearby answer
- Wake-up time if you sleep at 8 PMRelated answer
- Wake-up time if you sleep at 8:30 PMRelated answer
- Wake-up time if you sleep at 9 PMRelated answer
- Wake-up time if you sleep at 9:30 PMRelated answer
Frequently asked questions
Is 1 AM a good bedtime for an 8:45 AM alarm?
Yes, for most adults. Allowing 15 minutes to fall asleep, a 1:00 AM (01:00) bedtime gives five full cycles, or 7.5 hours of sleep, before 8:45 AM.
What if I go to bed at midnight and wake at 8:45 AM?
You would get about 8 hours 30 minutes of sleep, ending partway through a cycle. See wake-up times if you sleep at midnight for alarm times that fit better.
What time should a teenager go to bed to wake up at 8:45 AM?
Teenagers are recommended 8–10 hours of sleep, so 11:30 PM (23:30), giving 9 hours, is the better fit. A 1:00 AM bedtime gives 7.5 hours, which is below the teen range.
Related calculators
Bedtime calculator
Enter any wake-up time to see bedtimes that let you wake between sleep cycles.
Wake-up time calculator
Going to bed now or at a set time? Find wake-up times that land at the end of a cycle.
Sleep needs by age
See the recommended hours of sleep for any age, from newborns to older adults.
Sleep debt calculator
Add up the last seven nights and see how far you are from your sleep target.
Sources
- National Institute of Neurological Disorders and Stroke. Brain Basics: Understanding Sleep.
- Watson NF, et al. Recommended Amount of Sleep for a Healthy Adult: A Joint Consensus Statement of the American Academy of Sleep Medicine and Sleep Research Society. Journal of Clinical Sleep Medicine, 2015;11(6):591–592. doi:10.5664/jcsm.4758.
- Hirshkowitz M, et al. National Sleep Foundation’s sleep time duration recommendations: methodology and results summary. Sleep Health, 2015;1(1):40–43. doi:10.1016/j.sleh.2014.12.010.
- Centers for Disease Control and Prevention. About Sleep.
When to seek help
Talk to a doctor if you:
- regularly take longer than 30 minutes to fall asleep, or wake in the night and can’t get back to sleep;
- snore loudly, or someone notices you gasp or stop breathing while asleep;
- feel very sleepy during the day, especially while driving or working, despite enough time in bed.