Sleep Calculator

Wake up refreshed by timing your sleep to complete full 90-minute cycles.

How Sleep Cycles Work

Sleep happens in 90-minute cycles. Each cycle includes light sleep, deep sleep, and REM (dream) sleep. Waking up in the middle of a cycle leaves you feeling groggy, while waking up between cycles feels natural and refreshed.

The Science

  • Average sleep cycle: 90 minutes
  • Recommended cycles per night: 5-6 cycles (7.5-9 hours)
  • Time to fall asleep: ~15 minutes for most people

Tips for Better Sleep

  • Keep a consistent sleep schedule, even on weekends
  • Avoid screens for 30+ minutes before bed
  • Keep your room cool (65-68°F / 18-20°C)
  • Limit caffeine after 2pm
  • Exercise regularly, but not too close to bedtime

Quick Reference: Sleep Times

Wake up at...Go to sleep at...
5:00 AM9:30 PM or 11:00 PM
6:00 AM10:30 PM or 12:00 AM
7:00 AM11:30 PM or 1:00 AM
8:00 AM12:30 AM or 2:00 AM
9:00 AM1:30 AM or 3:00 AM

Based on 5 or 6 complete sleep cycles (7.5 or 9 hours) plus 15 minutes to fall asleep.