Sleep Calculator: Best Bedtime and Wake-Up Time by Sleep Cycle
Free sleep calculator: find the best bedtime for the time you need to wake up, or the best wake-up time if you go to bed now, using 90-minute sleep cycles. See your night's sleep stages, an evening plan, nap times and your weekly sleep debt.
Fine-tune: time to fall asleep and cycle length
Most adults fall asleep in about 10–20 minutes and cycle every 90 minutes (anywhere from 80 to 110). Watch how rested you feel and adjust.
Go to bed at one of these times
What your night looks like
A typical night, not a measurement of you: deep sleep (N3) comes mostly in the first half, REM (dreaming) lengthens toward morning, which is why cutting the end of the night costs REM.
An evening plan for tonight
Quick naps
Your sleep debt this week
Type how long you slept each night (like 7:30 or 6.5). Leave a night blank to skip it.
How the sleep calculator works
Sleep runs in cycles of about 90 minutes, each moving through light sleep, deep sleep and REM (dream) sleep. Waking at the end of a cycle, in light sleep, usually feels easier than being pulled out of deep sleep, even if the total time is a little shorter. The calculator counts back (or forward) in whole cycles and adds the time you need to fall asleep (about 15 minutes by default):
wake-up time = bedtime + time to fall asleep + (number of cycles × 90 minutes)
Example: bed at 11:00 PM, 15 minutes to fall asleep, 5 cycles: 11:00 + 0:15 + 7:30 = 6:45 AM.
How much sleep do you need?
Hours per 24 hours, from the American Academy of Sleep Medicine and National Sleep Foundation. Needs vary by person: if you feel rested and alert without an alarm after the lower end, that may be yours.
Tips for falling asleep faster
- Keep a regular schedule, including weekends: a steady wake time is the strongest anchor for your body clock.
- Get bright light soon after waking and dim the lights in the evening.
- Stop caffeine about 6 hours before bed (its half-life is around 5 hours) and keep alcohol away from the last few hours.
- Keep the room cool, dark and quiet; put screens away about an hour before bed.
Questions
- Why 90 minutes?
- It is the average adult cycle; individual cycles range from about 80 to 110 minutes and change through the night. Use the slider to match yours.
- Is a nap bad for night sleep?
- Short naps (10–20 minutes) before mid-afternoon usually are not. Long or late naps can make it harder to fall asleep at night.
- Can I catch up on lost sleep?
- Partly. Sleeping an extra 30–60 minutes for several nights helps; chronic shortage takes longer to recover and is better avoided.
- Is my data private?
- Yes. Everything stays in this browser.
General information, not medical advice. See a doctor if you regularly cannot sleep, snore heavily, or stop breathing at night. Related: Clock · Time Zone Converter · Heart Rate Zone Calculator