Sleep Calculator
Calculate optimal bedtime and wake times based on sleep cycles
Calculator
Sleep Cycles Explained
Recommended Sleep: 7-9 hours
- Consistency is key - try to sleep and wake at the same time daily
- Avoid screens 30 minutes before bed (blue light affects melatonin)
- Keep your bedroom cool (65-68°F / 18-20°C is ideal)
- Limit caffeine intake after 2 PM
How to Use
Find your optimal sleep and wake times
Choose your mode
Select "I need to wake up at" or "I'm going to bed at"
Enter your time
Input your target wake-up or bedtime
View sleep cycles
See recommended times based on 90-minute sleep cycles
Sleep Cycle Formula
Optimal bedtime = Wake time - (90 min × cycles) - 15 min
Each sleep cycle is 90 minutes. Add 15 minutes to fall asleep. 5-6 cycles is optimal for adults.
Frequently Asked Questions
Adults need 7-9 hours of sleep per night. Teenagers need 8-10 hours, school-age children need 9-11 hours. Quality matters too - uninterrupted sleep through complete cycles is more restorative than fragmented sleep.
A sleep cycle lasts about 90 minutes and includes light sleep, deep sleep, and REM sleep. Waking up between cycles (rather than during deep sleep) helps you feel more refreshed. That's why sleeping 7.5 hours can feel better than 8 hours.
To wake up at 7am feeling refreshed, go to bed at 9:30pm (5 cycles), 11pm (4 cycles), or 12:30am (3 cycles). Add 15 minutes to fall asleep. The calculator shows optimal bedtimes for any wake-up time.
You might be waking during deep sleep rather than at the end of a cycle. Try adjusting your sleep time by 15-30 minutes. Other factors include sleep apnea, caffeine, blue light exposure, or inconsistent sleep schedule.