What time should I go to bed if I wake up at 12:00 am?

Waking at 12:00 am is a night-shift or early-flight schedule, and the arithmetic does not care: five cycles still means lights out at 4:15 pm, which for most people is the previous afternoon.

Why three times and not one

4:15 pm buys five cycles (7 h 30 min). If you can manage 2:45 pm, that is six cycles and 9 h — the top of the range the NSF panel recommends for adults. At 5:45 pm you get four cycles, 6 h — a one-night compromise, below the 7-hour floor the AASM sets for adults.

Each cycle runs light sleep, deep sleep, then REM. Ninety minutes is the average; the real figure drifts between 70 and 120 minutes, and the first cycle of the night is usually the shortest.

Walk through the night from a 4:15 pm lights-out: asleep by about 4:30 pm, into the first stretch of deep sleep around 4:50 pm, first REM period near 5:45 pm, the halfway point of the night at 8:15 pm, and the longest REM period of the night starting around 11:25 pm — which is what a 12:00 am alarm at the end of cycle 5 lets you finish.

All bedtimes for a 12:00 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 4:15 pm

Build in the fifteen minutes honestly: lights out at 4:15 pm means phone down at 4:15 pm, not "in bed, scrolling". If sleep has not come by 4:35 pm, the guidance from sleep medicine is to leave the bed, do something dull in dim light, and return when sleepy — the next clean boundary is 5:45 pm.

Try a different time