Tools
Sleep cycle calculator
Waking at the end of a sleep cycle tends to feel better than waking in the middle of one. Pick a wake-up time and this works backwards in ~90-minute cycles, with 15 minutes allowed for falling asleep.
9:45 pm
6 cycles · about 9 hours of sleep
Most adults land here
11:15 pm
5 cycles · about 7.5 hours of sleep
12:45 am
4 cycles · about 6 hours of sleep
2:15 am
3 cycles · about 4.5 hours of sleep
Honest small print: 90 minutes is a population average — real cycles run roughly 70 to 110 minutes and drift through the night, so treat these times as starting points to adjust by feel, not a prescription. Bedtime is free; bedding only helps at the margin. If overheating is what wakes you, start with the sleep-temperature guide.