Sleep Calculator — Best Bedtime & Wake-Up Times
A sleep calculator finds the best time to go to bed or wake up so you wake at the end of a sleep cycle, not in the middle of one. Sleep runs in roughly 90-minute cycles, and most adults need 5 to 6 cycles a night.
Go to bed at one of these times to wake at 07:00:
How it works
- Enter the time you need to wake up, or choose “I want to sleep now”.
- The calculator subtracts about 15 minutes to fall asleep, then counts back in 90-minute cycles.
- Pick a bedtime that gives you 5 or 6 full cycles — about 7.5 to 9 hours in bed.
Formula
Worked example
If you need to wake up at 7:00 AM, six full cycles means going to bed at 9:45 PM the night before (7:00 AM − 15 minutes − 9 hours). Five cycles gives 11:15 PM, four cycles gives 12:45 AM, and three cycles gives 2:15 AM.
Frequently asked questions
How many sleep cycles do I need per night?
Most adults need 5 to 6 full sleep cycles a night, which is about 7.5 to 9 hours in bed. Children and teenagers need more.
What is a 90-minute sleep cycle?
A sleep cycle is the journey from light sleep through deep sleep to REM sleep. It lasts about 90 minutes on average. Waking at the end of a cycle usually feels easier than waking in the middle of deep sleep.
What time should I go to bed to wake up at 7am?
For a 7:00 AM wake-up, go to bed at 9:45 PM for six cycles, or 11:15 PM for five cycles. Enter your own wake-up time above to get your exact bedtimes.
Is it better to sleep 6 or 8 hours?
It depends on your cycles. Six hours is four full cycles and can feel better than seven hours, which may wake you mid-cycle. Most adults do best with 7.5 to 9 hours.
How long does it take to fall asleep?
This calculator allows about 15 minutes to fall asleep, which is typical for healthy adults. If you regularly take much longer, a regular bedtime and less screen time before bed can help.
What is the best time to wake up?
The best wake-up time is one that ends a sleep cycle and fits your day. Count back in 90-minute steps from your alarm time to find a bedtime that works.