Wake up refreshed by completing full 90-minute sleep cycles.
We'll calculate the best times to fall asleep.
We'll calculate the best times to wake up.
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Each option = complete sleep cycles (no grogginess)
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Sleep cycle facts:
One cycle = 90 minutes · Adults need 5–6 cycles (7.5–9 hrs) · Teens need 6–7 cycles · Waking mid-cycle causes grogginess
The Sleep Calculator finds the best time to go to bed or wake up based on 90-minute sleep cycles. Waking during a cycle leaves you groggy — waking at the end of a cycle means you'll feel refreshed. Enter your wake-up time or bedtime to get your ideal sleep schedule.
Frequently Asked Questions
What is a sleep cycle?
A complete sleep cycle lasts about 90 minutes and includes light sleep, deep sleep and REM sleep. Most people complete 4–6 cycles per night.
How many hours of sleep do I need?
Adults generally need 7–9 hours (5–6 complete cycles). Teenagers need 8–10 hours. Children need more. Consistently getting less than 7 hours increases health risks.
Why do I wake up tired even after 8 hours?
You may have woken mid-cycle. Try adjusting your alarm by 30–45 minutes to land at the end of a cycle instead.
What is the best time to go to sleep?
It depends on your wake-up time. Work backwards in 90-minute blocks. If you wake at 6:30am, ideal bedtimes are 11pm, 9:30pm or 8pm.