Sleep Calculator
Find the best time to go to bed or wake up based on 90-minute sleep cycles, so you wake up feeling refreshed.
About the Sleep Calculator
Waking up in the middle of a deep sleep cycle leaves you groggy, even after a long night. The sleep calculator times your bedtime or alarm to the end of a 90-minute sleep cycle, so you wake up between cycles and feel more alert.
How to Use the Sleep Calculator
- Choose whether you know your wake-up time or your bedtime.
- Enter the time.
- Press Calculate to see the best times, based on 4 to 6 sleep cycles.
Formula and How It Works
One sleep cycle lasts about 90 minutes. Most adults need 5 or 6 cycles (7.5 to 9 hours). The calculator also adds 15 minutes, the average time it takes to fall asleep.
Frequently Asked Questions
How many hours of sleep do adults need?
Adults need 7–9 hours a night. Teenagers need 8–10 hours and school-age children 9–12 hours.
Are sleep cycles always 90 minutes?
They range from about 80 to 120 minutes and vary through the night, so treat the times as a helpful guide.
Results are estimates for general information and are not medical or veterinary advice. Please speak to a qualified professional about your own situation.