Sleep Calculator

A sleep cycle is a ~90-minute period during which your body moves through different stages of sleep: light sleep, deep sleep, and REM (dream) sleep. Most adults experience 4-6 complete cycles per night. Waking up at the end of a cycle (during light sleep) helps you feel more refreshed than waking mid-cycle.

Most adults need 7-9 hours of sleep (4-6 cycles). Teenagers need 8-10 hours, and children need even more. However, quality matters as much as quantity—5 complete cycles (7.5 hours) often feels better than 8 hours interrupted mid-cycle.

You're likely waking up in the middle of a sleep cycle. 8 hours = 5.33 cycles, meaning your alarm might catch you during deep sleep. Try sleeping 7.5 hours (5 cycles) or 9 hours (6 cycles) instead. This calculator helps you find times that align with complete cycles.

For a 7:00 AM wake time, optimal bedtimes are: 9:45 PM (6 cycles, 9h), 11:15 PM (5 cycles, 7.5h), or 12:45 AM (4 cycles, 6h). These times include 15 minutes to fall asleep. Use our calculator above for your specific wake time!

15 minutes is the average, but it varies. If you fall asleep faster (5-10 min), go to bed slightly later. If it takes you longer (20-30 min), adjust earlier. Consistently falling asleep in under 5 minutes may indicate sleep deprivation; over 30 minutes could suggest insomnia.

Key tips: Keep a consistent sleep schedule (even weekends). Avoid screens 1 hour before bed. Keep your room cool (65-68°F / 18-20°C), dark, and quiet. Limit caffeine after 2 PM. Exercise regularly, but not within 3 hours of bedtime. Avoid large meals before sleep.