Sleep Cycle Calculator
See a wake-up time or bedtime that lands at the end of a sleep cycle.
Calculating a sleep time
How this number is chosen
A full night of sleep is a series of cycles. A typical cycle lasts about 90 minutes. Most people also need a little while to fall asleep, so this calculator adds 15 minutes before the cycles begin.
The time you see first is 5 cycles: 15 minutes to fall asleep, then 7 hours 30 minutes asleep. For most adults, that sits in the middle of the usual 7–9 hour range. Four cycles is a shorter night (6 hours asleep). Six cycles is a longer one (9 hours asleep).
If you are going to bed, the result is a wake-up time. If you already know when you have to be up, switch the calculator and the result becomes a bedtime. Either way, the time lands at the end of a cycle instead of in the middle of one.
What a sleep cycle is
Each cycle moves through lighter sleep, deep sleep, and REM sleep. REM is the stage most associated with vivid dreams. Early in the night, cycles contain more deep sleep. Toward morning, they contain more REM.
Waking at the end of a cycle usually means the alarm finds you in lighter sleep. Waking in the middle of deep sleep is more likely to feel abrupt. Cycle length is only an average, though. Yours may be shorter or longer than 90 minutes, and it can change through the night. Use the time as a plan, not as a measurement of your REM sleep.
How much sleep adults need
Most adults do well with 7–9 hours of sleep. Five cycles (7 hours 30 minutes, plus the time it takes to fall asleep) is the suggestion highlighted here because it lands in that range. A 6 hour night can be enough on occasion. A 9 hour night is reasonable if you are catching up, or if you already know you need more.
Teenagers often need more than adults, closer to 8–10 hours. If that is you, choose the 6 cycle time. Older adults often stay near the same 7–9 hour range, even when the night is more broken.
Frequently Asked Questions
How does the sleep cycle calculator work?
It adds or subtracts complete 90-minute cycles, plus 15 minutes to fall asleep. If you are going to bed, it gives you a wake-up time. If you set a wake-up time, it gives you a bedtime. The suggested time uses 5 cycles, which is 7 hours 30 minutes asleep.
What time should I go to bed if I wake up at 7:00 am?
For 5 cycles, get into bed at 11:15 pm. That assumes 15 minutes to fall asleep and 7 hours 30 minutes asleep. Four cycles would be 12:45 am. Six cycles would be 9:45 pm.
How long is a sleep cycle?
About 90 minutes for many adults. Real cycles often fall somewhere between 90 and 110 minutes, and the first cycles of the night are sometimes shorter. This calculator uses 90 minutes so the answer stays simple.
Is this a REM sleep calculator?
It plans around full cycles, which include REM sleep. It cannot see your stages of sleep. Later cycles usually hold more REM, so a wake time at the end of the last cycle is often near a lighter, dream-rich part of the night. That is a general pattern, not a reading of your night.
How much sleep do adults need?
Most adults need about 7 to 9 hours. The highlighted result is 7 hours 30 minutes of sleep, after 15 minutes to fall asleep. Teenagers often need closer to 8 to 10 hours, so the 6-cycle time is a better target for them.
If a dream stuck with you, you can interpret it.