Sleep Time Calculator
Enter when you went to bed and when you woke up. See total sleep time, the number of 90 minute cycles, and whether it is enough for your age.
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Sleep time calculator
A sleep time calculator tells you how long you slept between going to bed and waking up, and how many 90 minute cycles that adds up to. Seven or more hours is the target for adults.
Enter the time you went to bed and the time you woke up. Add how long you took to fall asleep if you know it. The calculator shows total sleep, cycles and whether the night fits the recommended range for your age group.
What sleep time means
Sleep time is the number of hours you actually spend asleep. It is different from time in bed. If you lie down at 11:00 PM, fall asleep at 11:20 PM and wake at 7:00 AM, your time in bed is 8 hours but your sleep time is about 7 hours 40 minutes. Counting only the hours between lights out and the alarm hides that gap, so this calculator lets you subtract the time you take to fall asleep.
Sleep time also helps you see patterns. A person who goes to bed at midnight on weekdays and 2:00 AM on weekends is changing their body clock twice a week, which is often called social jet lag. You can measure that with the social jet lag calculator.
Sleep time table: bedtime and wake up time
This table shows time in bed for common bedtimes and wake up times. Take off the time you need to fall asleep to get actual sleep.
| Bedtime | Wake at 6:00 AM | Wake at 7:00 AM | Wake at 8:00 AM |
|---|---|---|---|
| 9:00 PM | 9 h 00 min | 10 h 00 min | 11 h 00 min |
| 10:00 PM | 8 h 00 min | 9 h 00 min | 10 h 00 min |
| 11:00 PM | 7 h 00 min | 8 h 00 min | 9 h 00 min |
| 12:00 AM | 6 h 00 min | 7 h 00 min | 8 h 00 min |
| 1:00 AM | 5 h 00 min | 6 h 00 min | 7 h 00 min |
| 2:00 AM | 4 h 00 min | 5 h 00 min | 6 h 00 min |
Is your sleep time enough
The American Academy of Sleep Medicine and the Sleep Research Society say adults should regularly sleep 7 or more hours. The National Sleep Foundation panel gave a wider range of 7 to 9 hours for adults aged 18 to 64, and 7 to 8 hours for adults over 65. Teenagers need 8 to 10 hours and school age children need 9 to 12 hours.
Short sleep adds up. In a well known laboratory study (Van Dongen and colleagues, 2003), volunteers limited to 6 hours in bed a night for two weeks showed attention lapses comparable to up to two nights without any sleep, while rating themselves as only slightly sleepy. If your sleep time is below your range for several nights, the sleep debt calculator shows how much to recover.
How to lengthen your sleep time
- Fix the wake up time first. A steady alarm sets your body clock more reliably than a steady bedtime.
- Work backward from that alarm with the bedtime calculator to find a bedtime that gives 5 cycles.
- Shift bedtime earlier by 15 minutes every few nights, not by two hours at once.
- Use morning light and keep caffeine to the first half of the day.
- Keep the bedroom cool, dark and quiet. See the sleep hygiene checklist.
Frequently asked questions
What is a sleep time calculator?
It measures how long you slept from your bedtime and wake up time, shows the number of 90 minute cycles and compares the result with recommended hours for your age group.
How do I calculate my sleep time?
Subtract your bedtime from your wake up time, then remove the minutes you took to fall asleep. Bed at 11:00 PM and awake at 7:00 AM is 8 hours in bed, or about 7 hours 45 minutes of sleep with 15 minutes to drift off.
How many hours is a good sleep time?
Adults should aim for 7 or more hours. Teenagers need 8 to 10 hours and school age children need 9 to 12 hours.
What is the best sleep time for adults?
The best time is the one that gives you at least 7 hours and a steady schedule. Many adults find that 5 cycles, or 7.5 hours, works well.
Is 6 hours of sleep enough?
It is below the 7 hours recommended for adults. Occasional short nights happen, but regular 6 hour nights build sleep debt.
How many hours of sleep does an adult really need?
The American Academy of Sleep Medicine and Sleep Research Society recommend at least 7 hours a night for adults. The National Sleep Foundation suggests 7 to 9 hours for most adults and 7 to 8 hours for people 65 and older. Some people need more, and you can judge your own need by how you feel on days you are not sleep deprived.
Does a consistent sleep schedule really matter?
Yes. A regular sleep and wake time supports your body clock, which can make it easier to fall asleep and wake up. Large gaps between weekday and weekend times can leave you feeling jet lagged on Monday.
How many sleep cycles do I need per night?
Most adults do well with 5 cycles (about 7.5 hours) and some need 6 (about 9 hours). Four cycles, about 6 hours, is short for most people and is better used as an occasional fallback than a habit.