Sleep Calculator 💤
Find the best time to go to bed or wake up. SleepUtility counts in 90-minute sleep cycles so your alarm goes off between cycles, not in the middle of deep sleep.
SleepUtility Calculator
Calculate optimal sleep and wake times based on sleep cycles
How it works
Track Sleep Cycles
SleepUtility works by calculating natural sleep cycles, which usually last around 90 minutes each.
Sleep Science
SleepUtility uses science to help you avoid waking up during deep sleep, preventing grogginess.
Better Mornings
Wake up at the right time in your cycle to feel more refreshed and energized throughout the day.
How to use the sleep calculator
Pick the time you need to wake up and the calculator counts backwards in 90-minute sleep cycles to find your ideal bedtime. Or pick when you're going to bed (or tap Sleep Now) and it counts forward to the best times to set your alarm.
Each result lands at the end of a full cycle, when you're in light sleep and waking up is easiest. The calculator also adds 15 minutes, the typical time it takes to fall asleep, so the times reflect when you'll actually be asleep, not when you get into bed. Signed-in users can change that number in their sleep preferences.
Bedtimes for common wake-up times
Go to bed at one of these times to wake up between sleep cycles. Each column includes 15 minutes to fall asleep.
| Wake-up time | 6 cycles (9 h) | 5 cycles (7.5 h) | 4 cycles (6 h) |
|---|---|---|---|
| 5:00 AM | 7:45 PM | 9:15 PM | 10:45 PM |
| 5:30 AM | 8:15 PM | 9:45 PM | 11:15 PM |
| 6:00 AM | 8:45 PM | 10:15 PM | 11:45 PM |
| 6:30 AM | 9:15 PM | 10:45 PM | 12:15 AM |
| 7:00 AM | 9:45 PM | 11:15 PM | 12:45 AM |
| 7:30 AM | 10:15 PM | 11:45 PM | 1:15 AM |
| 8:00 AM | 10:45 PM | 12:15 AM | 1:45 AM |
How much sleep do you need?
Most adults need 7 to 9 hours a night, which is five or six full sleep cycles. Teenagers need 8 to 10 hours and school-age children 9 to 12. If you can only fit in four cycles (6 hours), waking at the end of a cycle still beats an alarm that cuts one short, but regular short nights add up to sleep debt.
Is your usual night long enough? 3 hours, 4 hours, 5 hours, 6 hours, 6.5 hours, 7 hours, 8 hours, 9 hours.
More free sleep tools
Nap Calculator
When to set your alarm for a power nap or a full-cycle nap.
Sleep Debt Calculator
How much sleep you owe from the past week, and how to pay it back.
REM Sleep Calculator
When each REM period happens and how much REM sleep you get.
Jet Lag Calculator
How long jet lag lasts and how to shift your sleep before you fly.
Sleep Efficiency Calculator
What share of your time in bed you actually spend asleep.
Sleep Schedule Calculator
A day-by-day plan to fix your sleep schedule or adjust to daylight saving time.
Caffeine Calculator
How much caffeine is left at bedtime and when to have your last coffee.
Chronotype Quiz
Five questions to find out if you are a morning lark or a night owl.
Frequently asked questions
What time should I go to bed if I wake up at 7 AM?
Go to bed at 9:45 PM for six sleep cycles (9 hours) or 11:15 PM for five cycles (7.5 hours). Both times include 15 minutes to fall asleep.
How long is a sleep cycle?
About 90 minutes on average, though a single cycle can run anywhere from roughly 70 to 120 minutes. Each one moves through light sleep, deep sleep and REM sleep.
Why does the calculator add 15 minutes?
Most people take 10 to 20 minutes to fall asleep. Adding 15 minutes means the cycles are counted from when you actually fall asleep, not from when you get into bed. Signed-in users can set their own number.
Is this sleep calculator free?
Yes. SleepUtility is free to use without an account and shows no ads. An optional free account saves your personal fall-asleep time.