The best time to wake up is at the end of a sleep cycle, not in the middle of one. Each cycle lasts about 90 minutes. This calculator finds the ideal wake or sleep times to keep you feeling refreshed.
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We calculate the optimal times based on 90-minute sleep cycles.
These times align with the end of a 90-minute sleep cycle.
| Cycles | Sleep Duration | Sleep At | Quality |
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Sleep is not uniform. You cycle through several stages during the night: light sleep (N1, N2), deep sleep (N3, slow-wave sleep) and REM (rapid eye movement) sleep. Each full cycle takes approximately 90 minutes.
Waking up during deep sleep (N3) or early in a REM stage leaves you feeling groggy and disoriented: a phenomenon called sleep inertia. Waking at the end of a light sleep phase means your brain has already begun the natural waking process, so you feel alert almost immediately.
Most adults need 5 to 6 complete cycles per night, which equals 7.5 to 9 hours. The calculator includes 14 minutes to account for the average time most people take to fall asleep, though you can adjust this figure.