Sleep Tools
Simple, science-based calculators to help you sleep better and wake up more refreshed. All tools are free and work entirely in your browser.
Why Sleep Cycles Matter
Sleep is not one continuous state. It happens in cycles of roughly 90 minutes, each passing through light sleep, deep sleep, and REM sleep. Waking up at the end of a cycle feels far better than waking up in the middle of one — even if you slept fewer total hours.
This is why a person who sleeps 6 hours (4 complete cycles) can feel more rested than someone who sleeps 6.5 hours (waking mid-cycle). Our tools help you plan around this natural rhythm.
How to Use These Tools
- Sleep Calculator: Enter the time you need to wake up, and we show you the best times to go to bed.
- Sleep Cycle Calculator: Enter the time you go to bed, and we show you what time you will wake up after each full cycle.
Both tools assume it takes about 15 minutes to fall asleep. This is an average — adjust the input if you typically fall asleep faster or slower.
Frequently Asked Questions
How many hours of sleep do I really need?
Most healthy adults need 7–9 hours per night. That works out to 5 or 6 complete sleep cycles. Individual needs vary based on age, activity level, and health.
Is it better to sleep 7.5 hours or 9 hours?
Both are healthy. 7.5 hours = 5 complete cycles, 9 hours = 6 cycles. The best option depends on how you feel. What matters most is waking at the end of a cycle, not in the middle.
Can these tools diagnose a sleep problem?
No. They are educational calculators. If you have ongoing trouble sleeping, please consult a qualified healthcare professional.