Sleep happens in roughly 90-minute cycles, and waking at the end of a cycle tends to feel more refreshing than waking mid-cycle. This tool estimates total time in bed for a chosen number of cycles, including time to fall asleep.
Sample input: Number of 90-minute cycles: 5
Total sleep needed: 7.8 (5 cycles (incl. 15-min latency))
Planning 5 sleep cycles of 90 minutes plus 15 minutes to fall asleep means about 7.8 hours in bed — a full, restorative night. To wake refreshed, time your alarm to the end of a cycle.
A full sleep cycle averages about 90 minutes and moves through light sleep, deep sleep, and REM. Adults typically complete four to six cycles per night.
Waking at the end of a cycle, in lighter sleep, usually feels easier than waking from deep sleep mid-cycle. We add about 15 minutes of sleep-onset latency, the average time it takes to fall asleep.
The CDC recommends at least 7 hours per night for adults, which is roughly five 90-minute cycles. Teenagers and children need more.
No. Cycle length varies between people and across the night, typically from 70 to 120 minutes. Use the estimate as a planning guide rather than a precise schedule.