An 11:30 am bedtime is a morning start, so none of the cycle options land in a conventional alarm window: four cycles ends at 5:44 pm, five at 7:14 pm and six at 8:44 pm. If you are on shifts, pick whichever fits the rota.
How this is worked out
Sleep runs in cycles of roughly 90 minutes, moving from light sleep into deep sleep and then REM and back out again. Waking at the end of a cycle means waking out of light sleep, which usually feels better than an alarm going off in the middle of deep sleep. We add 14 minutes for falling asleep, then count whole 90-minute cycles from there.
Limitations
Ninety minutes is an average, not your number. Real cycles run about 70 to 120 minutes and lengthen through the night, so the six-cycle time is a much looser target than the four-cycle one. Treat any of these as a window of about three quarters of an hour rather than a time to the minute. The 14-minute allowance for falling asleep is the same kind of average; if you routinely take half an hour, every time on this page is sixteen minutes out until you change it on the sleep cycle calculator.
Total sleep matters more than boundary timing. Do not trade an hour of sleep for a tidier alarm, and do not stay up to reach a cycle boundary you have already missed.
This page does arithmetic on a wall clock. It does not measure your sleep, it cannot tell you how much you need, and it is not medical advice. Persistent tiredness that a better bedtime does not fix — insomnia, sleep apnoea, restless legs, shift-work disorder — is common, treatable, and belongs with a doctor rather than with a calculator.