If I go to bed at 8:00 PM, what time should I wake up?
Falling asleep around 8:15 PM, the best wake-up times are 3:45 AM (5 cycles) or 5:15 AM (6 cycles), so your alarm lands at the end of a 90-minute cycle.
Best wake-up times after a 8:00 PM bedtime
| Wake up at | Cycles | Total sleep |
|---|---|---|
| 5:15 AM — best | 6 | 9 hours |
| 3:45 AM | 5 | 7.5 hours |
| 2:15 AM | 4 | 6 hours |
These assume about 15 minutes to fall asleep, so you are actually asleep by 8:15 PM. A 3:45 AM alarm completes 5 full cycles for a standard work morning; 5:15 AM completes all 6 for the fullest night.
How long is sleep from 8:00 PM?
From a 8:00 PM bedtime, five 90-minute cycles plus the time to fall asleep brings you to 3:45 AM (about 7.5 hours of sleep), and six cycles to 5:15 AM (about 9 hours). Four cycles gives a shorter 2:15 AM wake-up (~6 hours) if you have to be up early. Because each of these alarms lands on a cycle boundary — your lightest stage of sleep — getting up feels far less of a struggle.
Making 8:00 PM work as a bedtime
Keeping a 8:00 PM bedtime is mostly about the run-up: wind down with the lights low, put screens away for the hour beforehand, and keep the bedroom cool. Repeat the same cycle-aligned wake time every morning and the routine locks in fast. Working from a fixed alarm time instead? Open the matching wake-up page and it will count back to the bedtime for you.
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