Sleep calculator / Hours of sleep
Hours of Sleep Calculator
See exactly how many hours of sleep you'll get before your alarm, and whether it wakes you in the middle of a sleep cycle.
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How many hours of sleep will I get?
Count the time from when you get into bed to when your alarm goes off, then subtract the time it takes you to fall asleep, usually 10 to 20 minutes. 11 PM to 7 AM is 8 hours in bed, or about 7 hours 45 minutes of sleep. The calculator does this for you and also checks whether your alarm lands at the end of a 90-minute sleep cycle or in the middle of one.
Hours of sleep chart
Time in bed between common bedtimes and wake-up times. Subtract about 15 minutes for falling asleep to get your actual sleep.
| Bedtime | Up at 5:00 AM | Up at 6:00 AM | Up at 7:00 AM | Up at 8:00 AM |
|---|---|---|---|---|
| 9:00 PM | 8h | 9h | 10h | 11h |
| 10:00 PM | 7h | 8h | 9h | 10h |
| 11:00 PM | 6h | 7h | 8h | 9h |
| 12:00 AM | 5h | 6h | 7h | 8h |
| 1:00 AM | 4h | 5h | 6h | 7h |
| 2:00 AM | 3h | 4h | 5h | 6h |
Adults need at least 7 hours of actual sleep, so aim for about 7 hours 15 minutes in bed or more. Not sure how much you need? See sleep needs by age.
Is my alarm going to wake me mid-cycle?
Sleep runs in cycles of about 90 minutes. Waking at the end of one, in light sleep, usually feels easier than waking from deep sleep in the middle of one. If your alarm is close to a cycle boundary, the calculator tells you; if not, it suggests the nearest cycle-friendly alarm times. To plan from scratch, use the sleep calculator.
What if I'm not getting enough?
- Move bedtime, not your alarm. A steady wake-up time keeps your body clock on track. How to go to bed earlier.
- Add it up over the week. Short nights stack up into sleep debt. Check your sleep debt.
- Check your caffeine. Late coffee can keep you up past your planned bedtime. Find your cutoff.
Frequently asked questions
How many hours of sleep is 11pm to 7am?
8 hours in bed. After about 15 minutes to fall asleep, that is roughly 7 hours 45 minutes of sleep, which is within the 7 to 9 hours adults need.
How many hours of sleep is 10pm to 6am?
8 hours in bed, or about 7 hours 45 minutes of actual sleep.
How many hours of sleep is 11pm to 6am?
7 hours in bed, or about 6 hours 45 minutes of sleep. That is just under the 7-hour minimum for adults.
How many hours of sleep is 12am to 8am?
8 hours in bed, or about 7 hours 45 minutes of sleep.
How many hours of sleep will I get if I sleep now?
Tap "I'm going to sleep now" in the calculator above and set your alarm time. It counts the hours from right now, subtracts time to fall asleep, and tells you how many sleep cycles you will get.
Related reading
- How Long Before Bed Is It OK to Work Out?Finish a hard workout at least 1 hour before bed, and 2 or more hours is safer. Moderate evening exercise generally doesn't hurt sleep.4 min read
- How Long Before Bed Should You Eat? The 3-Hour Rule, ExplainedFinish a full meal about 3 hours before bed, and at least 2 hours if you get heartburn. A small snack closer to bedtime is usually fine.4 min read
- How Long Before Bed Should You Stop Drinking Water?Ease off fluids about 2 hours before bed if you wake up to pee, and cut caffeine and alcohol earlier. When night urination is worth a doctor visit.4 min read
More free sleep tools
All completely free, no sign-up.
- Sleep CalculatorBest bedtime or wake-up time, based on 90-minute sleep cycles.
- Nap CalculatorWhen to set your alarm for a power nap or a full-cycle nap.
- Sleep Debt CalculatorHow much sleep you owe this week, and how to pay it back.
- Caffeine Cutoff CalculatorHow much caffeine is still in you at bedtime, and your latest cup.
- Sleep Needs by AgeRecommended hours for every age, from newborns to over-65s.
- Sleep Efficiency CalculatorWhat share of your time in bed you actually spend asleep.
- Shift Work Sleep CalculatorWhen to sleep and stop caffeine around any shift, including nights.
- Jet Lag CalculatorDays to adjust, plus a shift-before-you-fly schedule.
These results are general estimates, not medical advice. Everyone's sleep is a little different. If you're often exhausted despite enough time in bed, snore loudly, or have been told you stop breathing in your sleep, see a doctor.