What time should I go to bed if I wake up at 11:45 am?

Waking at 11:45 am is a late start, which means the bedtime that gives five full cycles, 4:00 am, is after midnight — fine on a day off, harder on a schedule.

Why three times and not one

The middle option, 4:00 am, is five cycles and 7 h 30 min of actual sleep; 2:30 am is six cycles and 9 h. Both sit inside the adult range. The 5:30 am option is 6 h: enough to get through the day, not enough to do it twice.

Sleep moves from light sleep into deep sleep and then REM, and one pass takes about 90 minutes — anywhere from 70 to 120 depending on the person and the point in the night. That spread is why these are windows, not appointments.

In clock terms: lights out 4:00 am, asleep around 4:15 am, deepest sleep of the night between roughly 4:35 am and 5:45 am, the night's midpoint at 8:00 am, and REM building toward 11:10 am. The 11:45 am alarm lands as cycle 5 closes, so you are likely in light sleep rather than deep.

All bedtimes for a 11:45 am alarm

Formula: bedtime = wake time − (cycles × 90 min) − 15 min · adult range from the NSF 2015 panel and the AASM/SRS 2015 consensus · methodology

If you can't fall asleep by 4:00 am

If 4:00 am comes and your mind is still running, aim for the next cycle boundary at 5:30 am instead of counting the minutes. Ten to twenty minutes to fall asleep is normal; much longer, repeatedly, is worth a conversation with a clinician rather than a calculator.

Try a different time