Waking up groggy often has less to do with how long you slept and more to do with when you woke up. Sleep runs in cycles of about 90 minutes, and waking at the end of a cycle feels easier. This sleep cycle calculator shows the best bedtimes if you know when you must wake up, or the best alarm times if you are heading to bed now. It also highlights the recommended hours for your age group.
How to use:
- Choose “I want to wake up at” or “I’m going to bed at”.
- Enter your time and how long you usually take to fall asleep.
- Pick your age group and a 12-hour or 24-hour clock.
- Click Calculate and choose one of the suggested times. Five or six cycles is ideal.
Q: How long is one sleep cycle?
A: About 90 minutes on average, although it can vary from person to person and from night to night.
Q: How many sleep cycles do I need?
A: Most adults feel best with 5 to 6 cycles, which is 7.5 to 9 hours. Four cycles (6 hours) can work occasionally, but it is short for regular use.
Q: Why do I feel tired even after sleeping 8 hours?
A: You may have woken in the middle of a deep sleep stage, which can cause grogginess. Waking at the end of a cycle usually feels easier. Sleep quality, stress, caffeine and alcohol also play a part.
Q: Why does the calculator ask how long I take to fall asleep?
A: Sleep cycles only start once you are asleep. The calculator adds your fall-asleep time (15 minutes by default) so the suggested times are more accurate.
