Sleep Cycle Calculator (Best Time to Wake Up or Go to Bed)
Wake-up times from your bedtime, or bedtimes from your alarm, in whole 90-minute sleep cycles.
Inputs
| Cycles | Asleep | Wake at |
|---|---|---|
| 6 cycles | 9h 00m | 08:15 |
| 5 cycles | 7h 30m | 06:45 |
| 4 cycles | 6h 00m | 05:15 |
| 3 cycles | 4h 30m | 03:45 |
- Working
- 23:00 + 15 min to fall asleep + 5 × 90 min = 06:45
- Asleep by about
- 23:15
- Time asleep
- 7h 30m
- CDC adult guidance
- 7 hours or more — meets it
Use this calculator on your own site
Free embed
- Two lines of HTML, unlimited views
- Shows a small CalculateEveryday bar, with a credit link under the calculator
What each Sleep Cycle input means
- I know my
- Wake-up times from a bedtime, or bedtimes from the time you must get up.
- That time
- Your bedtime or your alarm time, depending on the mode.
- Sleep cycles
- How many 90-minute cycles to plan for: five is 7.5 hours of sleep, which meets the CDC's 7-hour adult guidance; six is 9 hours.
- Minutes to fall asleep
- Minutes you usually take to fall asleep, 15 by default. Raise it if you tend to lie awake for longer.
Sleep Cycle formula
wake time = bedtime + minutes to fall asleep + cycles × 90 min · bedtime = alarm − cycles × 90 min − minutes to fall asleep
Sleep runs in cycles — light sleep, deep sleep, REM — that the NHLBI puts at 80 to 100 minutes each, four to six of them a night. Waking at the end of a cycle, from light sleep, tends to feel easier than being pulled out of deep sleep in the middle of one, which is the whole idea behind timing sleep in whole cycles. Using the 90-minute convention, five cycles is 7½ hours and six is 9. Add the time it takes you to drop off (15 minutes is a common allowance; use your own), and the page gives the wake-up time for a bedtime, or, run the other way, the bedtime for an alarm. The table under the result lists the other cycle counts so you can see the nearest good options, and the CDC's guidance that adults need 7 hours or more is checked against the sleep actually planned.
Sleep Cycle worked example
In bed at 23:00 and asleep by about 23:15. Five cycles of 90 minutes is 7 h 30 min, so the alarm for the end of the fifth cycle is 06:45; six cycles would be 08:15 and four 05:15. Run backwards for a 06:30 alarm: 06:30 minus 7 h 30 min minus 15 minutes puts bedtime at 22:45.
More Sleep Cycle examples
To wake at 06:30 after five cycles, allowing 20 minutes to fall asleep: 06:30 − 7 h 30 min − 20 min = 22:40 in bed, asleep by about 23:00.
Where the Sleep Cycle calculator can give the wrong answer
- Ninety minutes is a convention, not your number. Cycles run 80 to 100 minutes and change through the night — earlier cycles are heavier in deep sleep, later ones in REM — so the boundary an hour after bedtime lands a little differently for everyone.
- The fall-asleep allowance is a guess. If you regularly lie awake for half an hour, enter 30; if you drop off at once, enter 0. The wake time moves by exactly that much.
- Four cycles is 6 hours, under the CDC's 7-hour guidance for adults, and the page says so. Timing the wake-up well does not make up for too little sleep.
- Alarms, noise, light and a partner's movement wake people regardless of cycle. The calculator plans; it does not control what happens at 05:00.
- Times use a 24-hour clock and wrap past midnight, so a 01:00 bedtime with five cycles wakes at 08:45 the same morning.
Spotted a mistake? Tell us
Sleep Cycle FAQ
- With 15 minutes to fall asleep and 90-minute cycles: 05:15 after four cycles (6 h), 06:45 after five (7½ h) or 08:15 after six (9 h). Five or six cycles meet the CDC's 7-hour guidance for adults; four does not.
- For five cycles, 22:15 — 06:00 minus 7 h 30 min of sleep minus 15 minutes to fall asleep. For six cycles, 20:45; for four, 23:45. Choose 'Alarm time → when to go to bed' and enter 06:00.
- About 90 minutes is the planning figure; the NHLBI gives a range of 80 to 100 minutes, with four to six cycles in a night. Each cycle moves through light sleep, deep sleep and REM, and the mix shifts as the night goes on.
- Five or six for most adults: 7½ to 9 hours, in line with the CDC's 7-hours-or-more guidance. Teenagers need 8–10 hours, which is six cycles or more. Four cycles (6 hours) is an occasional short night, not a plan.
- It helps with grogginess on waking (sleep inertia), which is worse when an alarm interrupts deep sleep. It does not reduce the amount of sleep you need. The best use of the page is to pick a bedtime that gives enough whole cycles before an alarm you cannot move.