Online Timer Stuon Product of Stuon

Sleep Calculator

Line your alarm up with the end of a sleep cycle instead of the middle of one.

How to use the sleep calculator

  1. Choose whether you know your wake-up time, your bedtime, or want to sleep now.
  2. Adjust how long you usually take to fall asleep (15 minutes is typical).
  3. Pick one of the suggested times. Five or six cycles (7.5–9 hours) suits most adults.

How it works

Sleep runs in cycles of roughly 90 minutes. Waking at the end of a cycle, rather than in deep sleep, usually feels easier.

Bedtime = wake-up time − time to fall asleep − (cycles × 90 min). For a 7:00 AM alarm: 7:00 − 0:15 − 7:30 = 11:15 PM for five cycles.

Wake up at6 cycles (9 h)5 cycles (7.5 h)4 cycles (6 h)
5:30 AM8:15 PM9:45 PM11:15 PM
6:00 AM8:45 PM10:15 PM11:45 PM
6:30 AM9:15 PM10:45 PM12:15 AM
7:00 AM9:45 PM11:15 PM12:45 AM
7:30 AM10:15 PM11:45 PM1:15 AM
8:00 AM10:45 PM12:15 AM1:45 AM

Frequently asked questions

What time should I go to bed to wake up at 6 AM?

Around 8:45 PM for six cycles, 10:15 PM for five, or 11:45 PM for four, assuming 15 minutes to fall asleep.

Is a sleep cycle always 90 minutes?

No. Cycles typically last 80–120 minutes and vary through the night and between people. 90 minutes is a useful average; change the cycle length if you know yours.

How much sleep do adults need?

Most adults need 7 or more hours a night. Treat the suggested times as a guide, not medical advice.

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