Sleep comes in ~90 minute cycles. Wake at the end of a cycle and you feel human. Wake in the middle and you feel like a raccoon who pays taxes.
Educational, not a diagnosis. Funny cycle names stay. The science still matters.
Adults generally need 7–9 hours. This tool uses 90-minute cycles plus your fall-asleep buffer. It is not medical advice. If you wake up like a goblin every day, start with the highlighted cycle.
A sleep calculator (also called a sleep cycle calculator or bedtime calculator) estimates when to go to bed or wake up using ~90-minute cycles. Most adults need 7–9 hours. Add the minutes it takes you to fall asleep. Five cycles is about 7.5 hours of sleep; six is about 9.
If I go to sleep now, use the “wake times if I sleep then” button. If you already know the alarm, use “bedtimes for that wake-up.” Waking at the end of a cycle usually feels better than waking mid-cycle. This is a planning tool, not a lab reading of your REM sleep and not medical advice.
Sleep usually arrives in ~90 minute cycles. We add your fall-asleep buffer, then list the cycle endings. Waking at the end of a cycle is easier than waking in the middle.
Most adults do best with 7–9 hours. The highlighted times here are the least miserable options in that range.
No. It is a timing helper only.