What time should I go to bed to wake up at 9:15 AM?
Go to bed at
1:31 AM
5 cycles · 7h 30m of sleep
12:01 AM
6 cycles
3:01 AM
4 cycles
4:31 AM
3 cycles
Fine-tune
Includes 14 minutes to fall asleep.
Questions
What time should I go to sleep to wake up at 9:15 AM?
Go to bed at 1:31 AM for 5 full sleep cycles (7 hours 30 minutes), or at 12:01 AM for 6 cycles (9 hours). Both assume about 14 minutes to fall asleep.
What's the latest bedtime for a 9:15 AM alarm?
3:01 AM gives 4 cycles (6 hours). That's under the 7 hours adults need, so keep it occasional.
Why not exactly 8 hours before 9:15 AM?
8 hours would likely end mid-cycle. 1:31 AM lines your alarm up with the end of your 5th roughly 90-minute cycle, when sleep is lightest.