Sleep Calculator
Find the best time to sleep or wake up based on 90-minute sleep cycles. Wake up feeling refreshed instead of groggy.
I need to wake up at
:(07:00 am)
Go to bed at
09:45 pm
6 cycles · 9.0 hrs
Recommended11:15 pm
5 cycles · 7.5 hrs
Recommended12:45 am
4 cycles · 6.0 hrs
02:15 am
3 cycles · 4.5 hrs
This calculator assumes it takes about 15 minutes to fall asleep. Each sleep cycle lasts roughly 90 minutes. For best results, maintain a consistent sleep schedule.
Frequently asked questions
- Why are sleep cycles 90 minutes?
- A complete sleep cycle — from light sleep through deep sleep and REM — takes roughly 90 minutes. Waking between cycles rather than in the middle of one helps you feel more refreshed.
- How many sleep cycles do I need?
- Most adults need 5 to 6 full cycles (7.5 to 9 hours) per night. Some people function well on 4 cycles, but consistently sleeping fewer than 5 cycles can affect health and performance.
- Does it matter when I go to sleep?
- Yes. Sleep before midnight tends to include more deep sleep, which is critical for physical recovery. Consistent sleep and wake times also improve overall sleep quality.