Work backwards through 90-minute cycles to a better bedtime or alarm
A sleep cycle runs about 90 minutes, and waking at the end of one usually feels easier, so the alarm goes after a whole number of cycles rather than mid-cycle. Falling asleep is assumed to take 15 minutes (most people take 10–20) and can be adjusted. Cycle length varies from person to person (70–120 minutes); if you are chronically short on sleep or drowsy by day, protect total duration before fine-tuning cycles.