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Wake Up Time
Recommended Bedtimes
9:45 PM
6 sleep cycles (9 hours of sleep)
11:15 PM
5 sleep cycles (7.5 hours of sleep)
12:45 AM
4 sleep cycles (6 hours of sleep)
Times include ~15 minutes to fall asleep
Understanding Sleep Cycles
One Sleep Cycle = 90 minutes
- Stage 1: Light sleep (5-10 min)
- Stage 2: True sleep (20 min)
- Stage 3: Deep sleep (20-40 min)
- REM: Dreaming (10-20 min)
Recommended Cycles by Age
- Adults: 5-6 cycles (7.5-9 hours)
- Teens: 6 cycles (9 hours)
- Children: 7 cycles (10-11 hours)
- Seniors: 5 cycles (7.5 hours)
Sleep Tips
Nap Calculator
Choose your nap type to see when to set your alarm:
Sleep Environment Checklist
Sleep Times
Best Bedtime
9:45 PM
6 cycles (9h)
Adults need 7-9 hours of sleep per night
Frequently Asked Questions
What is a sleep cycle?
A sleep cycle is approximately 90 minutes long and includes all stages of sleep: light sleep, deep sleep, and REM (dreaming) sleep. Most adults need 5-6 complete cycles (7.5-9 hours) per night. Waking between cycles helps you feel more refreshed.
Why do I feel groggy even after 8 hours of sleep?
You likely woke up in the middle of a sleep cycle, especially during deep sleep. Try adjusting your sleep time by 15-30 minutes to wake at the end of a cycle. Using this calculator helps you time your sleep to complete full cycles.
How much sleep do I really need?
Adults typically need 7-9 hours per night. However, quality matters as much as quantity. 5-6 complete sleep cycles (7.5-9 hours) is optimal. Some people function well on less, but most need at least 7 hours.
Does it take 15 minutes to fall asleep?
On average, it takes 10-20 minutes for healthy adults to fall asleep. This calculator uses 15 minutes as an average. If you consistently fall asleep instantly, you may be sleep-deprived. If it takes over 30 minutes, you may have insomnia.
What time should I go to bed?
The best bedtime depends on when you need to wake up. Count back in 90-minute cycles from your wake time, then add 15 minutes to fall asleep. For example, to wake at 7 AM after 6 cycles: 7 AM - 9 hours - 15 min = 9:45 PM.