Bedtime Calculator

Count back in 90-minute cycles from your wake time, plus 15 minutes to fall asleep. For a 6:30 AM wake-up: 5 cycles = 11:15 PM, 6 cycles = 9:45 PM. Six cycles (9 hours) is ideal for most adults.

Each sleep cycle lasts about 90 minutes and includes light sleep, deep sleep, and REM sleep. Waking at the end of a cycle (during light sleep) feels natural. Waking mid-cycle (during deep sleep) causes that groggy, disoriented feeling called sleep inertia.

Yes. Most people take 10-20 minutes to fall asleep (sleep latency). This calculator adds your fall-asleep time to ensure your actual sleep aligns with complete cycles. If you fall asleep in 5 minutes, that may indicate sleep deprivation.