Sleep Calculator
Optimize your sleep by waking up between sleep cycles.
I want to wake up at...
I'm going to bed at...
How it works: A full sleep cycle lasts about 90 minutes, and a good night's sleep consists of 5-6 complete cycles (7.5-9 hours). Waking up between cycles — rather than in the middle of one — helps you feel more refreshed. This calculator also accounts for the average time it takes to fall asleep.
About This Tool
Calculate the best times to fall asleep or wake up based on 90-minute sleep cycles. Waking between cycles leaves you groggy, while waking at the end of a cycle helps you feel refreshed.
How to Use
- Enter what time you need to wake up (or when you plan to fall asleep).
- The calculator shows optimal sleep and wake times based on 90-minute cycles.
- Aim for 5-6 complete cycles (7.5-9 hours) for the best rest.
Frequently Asked Questions
Why do I feel tired after 8 hours of sleep?
You may be waking in the middle of a sleep cycle. Try sleeping 7.5 hours (5 cycles) or 9 hours (6 cycles) instead, which aligns with natural cycle boundaries.
How long is one sleep cycle?
About 90 minutes on average, progressing through light sleep, deep sleep, and REM stages. Most adults need 5-6 complete cycles per night.