Vclock · Free Sleep Calculator
Wake-up time
Sleep comes in cycles of about 90 minutes, and most people need around 15 minutes to fall asleep. These are estimates, not medical advice.
Go to bed at one of these times
- 9:45 PM6 cycles · 9 hours of sleep· Recommended
- 11:15 PM5 cycles · 7.5 hours of sleep· Recommended
- 12:45 AM4 cycles · 6 hours of sleep
- 2:15 AM3 cycles · 4.5 hours of sleep
How the sleep calculator works
Sleep moves through cycles of light sleep, deep sleep and dream (REM) sleep. A full cycle lasts about 90 minutes, though it varies from person to person. Many people find it easier to wake up at the end of a cycle than in the middle of one.
Pick the time you need to wake up and the calculator counts back in 90 minute steps, adding about 15 minutes for you to fall asleep. Or enter the time you are going to bed, or press Sleep now, and it shows when to wake up.
How much sleep do I need?
Health agencies say most adults need at least 7 hours of sleep a night, and many do best with 7 to 9 hours. That is 5 or 6 cycles, which is why those results are marked Recommended. Children and teenagers need more.
Then set your alarm
Each result has a link to the matching online alarm clock page. For a short nap, a 20 minute timer helps you wake up before deep sleep. This is general information, not medical advice.
Questions
How does the sleep calculator work?+
It counts in sleep cycles of about 90 minutes and adds around 15 minutes to fall asleep. If you want to wake up at 7:00 AM, it suggests bedtimes of 9:45 PM, 11:15 PM, 12:45 AM and 2:15 AM.
How many sleep cycles do I need?+
Most adults feel best after 5 or 6 cycles, which is 7.5 to 9 hours. Four cycles (6 hours) can work for a short night, but it is less than most adults need.
What if I take longer than 15 minutes to fall asleep?+
Everyone is different. If you usually take 30 minutes, go to bed 15 minutes earlier than the time shown.
Is a 90 minute cycle exact?+
No. It is an average. Cycles can be shorter or longer, and they change through the night, so treat the times as a guide.
Is this medical advice?+
No. It is a simple planning tool. If you often sleep badly or feel tired all day, talk to a doctor.