Sleep Calculator
Calculate the best times to fall asleep and wake up based on 90-minute sleep cycles. Wake up refreshed by aligning your sleep with your natural cycles — completely free.
What time do you need to wake up?
Includes ~14 min to fall asleep
22:14
6 cycles · 9h
Optimal23:44
5 cycles · 7h 30m
Optimal01:14
4 cycles · 6h
02:44
3 cycles · 4h 30m
Tips for Better Sleep
- Go to bed and wake up at the same time every day, even on weekends
- Avoid screens (phone, TV, computer) at least 30 minutes before bed
- Stop consuming caffeine at least 6 hours before bedtime
- Keep your bedroom cool (15-19°C / 60-67°F) for optimal sleep
- Make your room as dark as possible — use blackout curtains or a sleep mask
How Sleep Cycles Work
Sleep occurs in 90-minute cycles, each containing light sleep, deep sleep, and REM (dream) stages. Waking up between cycles — rather than in the middle of one — helps you feel refreshed and alert. Most adults need 5-6 complete cycles (7.5-9 hours) per night for optimal health.
Frequently Asked Questions
A Sleep Calculator helps you find the best times to go to sleep or wake up based on 90-minute sleep cycles. It accounts for the average time it takes to fall asleep (about 14 minutes) and recommends times that align with the end of a sleep cycle, so you wake up feeling refreshed.
Sleep cycles are approximately 90-minute periods that repeat throughout the night. Each cycle includes light sleep, deep sleep, and REM sleep. Waking up at the end of a cycle (rather than in the middle) helps you feel more alert and less groggy.
Most adults need 7-9 hours of sleep per night, which equals 5-6 complete sleep cycles of 90 minutes each. The calculator highlights 5-6 cycle options as optimal, but individual needs may vary.
Yes, completely free with no registration. All calculations happen instantly in your browser — your data is never stored or sent anywhere.