Sleep Cycle Calculator
What time should I go to bed to wake up at 7:00 AM feeling rested?
Go to bed at 11:15 PM for five 90-minute sleep cycles (7.5 hours), or 9:45 PM for six cycles (9 hours), assuming about 15 minutes to fall asleep.
90-minute cycle estimate · 7–9 hours for adults (National Sleep Foundation, 2015) ·
Result
Go to bed at (5 cycles, 7 hr 30 min of sleep)
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This is an estimate, not medical advice. Real sleep cycles vary from about 70 to 120 minutes from person to person and night to night.
Something off with the result?
How it's calculated
90-minute cycle estimate · 7–9 hours for adults (National Sleep Foundation, 2015)
- One sleep cycle is estimated at 90 minutes (real cycles run about 70–120 minutes)
- Bedtime = wake-up time − cycles × 90 min − time to fall asleep
- Wake-up time = bedtime + time to fall asleep + cycles × 90 min
- Shows 3 to 6 cycles (4.5 to 9 hours) and marks 5 and 6 cycles, which fall within the 7–9 hours recommended for adults
- Source: Hirshkowitz M, et al. National Sleep Foundation's sleep time duration recommendations. Sleep Health 2015;1:40-43
- Check: wake at 7:00 AM, 15 minutes to fall asleep → 5 cycles means bed at 11:15 PM, 6 cycles means 9:45 PM
Frequently asked questions
How long is one sleep cycle?
About 90 minutes on average. Each night you move through light sleep, deep sleep and REM sleep several times, and one full round takes roughly 90 minutes, though it can run anywhere from about 70 to 120 minutes depending on the person and the night.
What time should I go to bed if I wake up at 6 AM?
If it takes you about 15 minutes to fall asleep, go to bed at 10:15 PM for five cycles (7.5 hours of sleep) or 8:45 PM for six cycles (9 hours). Change the wake-up time above to see your own options.
Is it bad to wake up in the middle of a sleep cycle?
Waking from deep sleep is what tends to leave you groggy. Timing your alarm for the end of a cycle, when sleep is lighter, is a simple way to make waking up feel easier. It is an estimate, not a guarantee, since your cycles are not exactly 90 minutes.
How many hours of sleep do adults need?
The National Sleep Foundation (2015) recommends 7 to 9 hours for adults 18 to 64 and 7 to 8 hours for adults 65 and older. In 90-minute cycles, five cycles (7.5 hours) or six cycles (9 hours) land in that range.
How long should it take to fall asleep?
Most people fall asleep within about 10 to 20 minutes, so the calculator uses 15 minutes by default. If you usually drop off right away, lower it; if you tend to lie awake, raise it.