Sleep Cycle Calculator – Best Time to Wake Up or Go to Sleep
Waking up in the middle of a sleep cycle leaves you groggy all day. Our sleep cycle calculator uses 90-minute sleep cycles to tell you exactly when to wake up — or when to go to bed — so you feel fully rested.
Sleep Cycle Calculator
How Sleep Cycles Work
Your sleep is divided into repeating 90-minute cycles of light sleep, deep sleep, and REM sleep. Waking at the end of a cycle means you wake in light sleep — feeling alert and refreshed.
Sleep Needs by Age
| Age Group | Recommended Sleep |
|---|---|
| Adults (18–64) | 7–9 hours (5–6 cycles) |
| Teenagers | 8–10 hours |
| Seniors (65+) | 7–8 hours |
Frequently Asked Questions
What is a sleep cycle?
A sleep cycle is approximately 90 minutes and consists of 4 stages: light sleep, deeper light sleep, deep sleep (N3), and REM.
Why do I feel worse after 8 hours than 7.5?
You woke mid-cycle — called sleep inertia. Sleeping 7.5 hours (5 complete cycles) often feels better than 8.
Should I use an alarm?
Time your alarm to the end of a cycle. Avoid snooze — it starts a new cycle you won't complete.