Sleep Calculator
Enter your wake-up time or bedtime to get matching bed or wake-up times for 4 to 6 sleep cycles of 90 minutes, with time to fall asleep included.
To wake up optimally rested:
21:46
6 Sleep Cycles
9 hours of sleep
Recommended23:16
5 Sleep Cycles
7.5 hours of sleep
Recommended00:46
4 Sleep Cycles
6 hours of sleep
Note: A sleep cycle lasts approximately 90 minutes.
- A sleep cycle lasts approx. 90 minutes
- 5-6 cycles are optimal (7.5 - 9 hours)
- Waking between cycles feels more refreshing
- Approx. 14 minutes falling asleep time included
Note: These calculations are for informational purposes only and do not replace professional tax or financial advice. All information without guarantee.
FAQ
Frequently Asked Questions
How much sleep do adults need?
Adults typically need 7-9 hours of sleep per night. Sleep cycles last about 90 minutes, so planning sleep in multiples of 90 minutes (e.g., 7.5 hours) can help you wake feeling refreshed.
What time should I go to bed?
Count back from your wake time in 90-minute sleep cycles. For a 6:30 AM alarm, ideal bedtimes are 9:00 PM (6 cycles), 10:30 PM (5 cycles), or midnight (4.5 cycles), plus 15 minutes to fall asleep.
Is the time it takes to fall asleep already included in the times shown?
Yes. The calculator plans full 90-minute sleep cycles and adds about 14 minutes to fall asleep. With a 7:00 AM alarm this means going to bed at 11:16 PM for 5 cycles (7.5 hours of sleep), at 9:46 PM for 6 cycles (9 hours) or at 12:46 AM for 4 cycles (6 hours). If you usually need much longer to fall asleep, go to bed correspondingly earlier.
Guide
What is the Sleep Calculator?
The sleep calculator computes optimal sleep and wake times based on sleep cycles of approximately 90 minutes.
How does the Sleep Calculator work?
Enter your desired wake-up time or bedtime. The calculator computes optimal times in 90-minute cycles so you wake at the end of a cycle and feel rested. The time to fall asleep (approx. 15 min) is factored in.
Key Data and Facts
Sleep cycle: approx. 90 minutes. Recommended cycles: 5-6 per night (7.5-9 hours). Recommended sleep for adults: 7-9 hours. Average time to fall asleep: 15 minutes.
Step-by-Step Guide
How to calculate optimal sleep times step by step: 1. Enter your wake-up time or your time of falling asleep: choose whether you want to calculate the optimal time of falling asleep or your wake-up time. 2. Account for the time it takes to fall asleep: the calculator adds about 15 minutes, the average time needed to fall asleep. 3. Understand sleep cycles: one sleep cycle lasts about 90 minutes and runs through light sleep, deep sleep and the REM phase. At the end of a cycle you wake up more easily and feel more rested. 4. Read off the recommended times: the calculator suggests 4-6 cycles: 4 cycles = 6 hours, 5 cycles = 7.5 hours (ideal for most adults), 6 cycles = 9 hours. 5. Example: wake-up time 6:30. Optimal times to fall asleep: 23:00 (5 cycles), 21:30 (6 cycles) or 00:30 (4 cycles). Minus 15 min. for falling asleep: go to bed at 22:45, 21:15 or 00:15.
Calculation Example
Wake-up time 6:30, 5 sleep cycles wanted: 5 x 90 min = 7.5 hours. Time to fall asleep: 23:00. Bedtime (minus 15 min): 22:45.
Sources
Official sources
Calculations are based on applicable German laws and official data:
Full methodology at Methodology.
Reviewed by Konstantin Iakovlev · Last updated:
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