Sleep Calculator
Find the best time to go to bed or wake up, based on 90-minute sleep cycles.
Advanced settings
Features
- Bedtimes for a set wake-up time, or wake-up times for a set bedtime
- Going to bed now? Get wake-up times from the current time
- Highlights the options that give 7 to 9 hours of sleep
- Adjustable cycle length and time to fall asleep, plus calendar reminders
How to Use
Choose I want to wake up at, I want to go to bed at, or I am going to bed now.
Pick the time, and if you like open Advanced settings to change the cycle length or how long you take to fall asleep.
Click Calculate, choose one of the times - the recommended ones give 7 to 9 hours of sleep - and add a reminder to your calendar.
About This Tool
Sleep Calculator suggests bedtimes and wake-up times that line up with the end of a sleep cycle, when sleep is lighter and waking up tends to feel easier. Enter the time you need to wake up and it counts back in whole 90-minute cycles, enter your bedtime and it counts forward, or tap I am going to bed now to use the current time. It allows for the time you take to fall asleep, highlights the options that give 7 to 9 hours of sleep, lets you adjust the cycle length, and can add a reminder to your calendar.
Frequently Asked Questions
Sleep runs in cycles of about 90 minutes. The calculator counts whole cycles back from your wake-up time, or forward from your bedtime, and adds the time you usually take to fall asleep. To wake at 7:00 AM after five cycles with 15 minutes to fall asleep, you would go to bed at 11:15 PM.
The CDC recommends 7 or more hours a night for adults aged 18 to 60, 7 to 9 hours for ages 61 to 64, 7 to 8 hours from 65, 8 to 10 hours for teenagers and 9 to 12 hours for children aged 6 to 12. The calculator marks the options that give adults 7 to 9 hours.
Waking from deep sleep in the middle of a cycle is more likely to leave you groggy, an effect called sleep inertia. Timing your alarm for the end of a cycle, when sleep is lighter, can help you wake up feeling clearer.
Only if you know your own pattern. Cycles average about 90 minutes but vary between people and through the night. If you regularly wake up just before your alarm, your cycles may be a little shorter; try 80 or 85 minutes.
Websites are not allowed to set a phone's alarm clock. Instead, Add reminder downloads a calendar event with an alert at that exact time, which opens in the calendar on any phone or computer.
No. It is a planning guide based on average sleep cycles. If you feel tired most days however long you sleep, or you snore loudly or wake up often, talk to a doctor.