Sleep Calculator
Suggested Bedtimes
Times use your selected cycle length and fall-asleep buffer; they cannot predict sleep stages. Choose enough total sleep. Shorter options are not adequate regular sleep targets for most adults.
Sleep breakdown
- Fall-asleep time
- 15 min
- Cycle length
- 90 min
- Target time
- —
Calculated Sleep Hours
Interval Details
- Bedtime
- 11:00 PM
- Wake-up time
- 7:00 AM
- Total time in bed
- 8h 00m
- Time to fall asleep
- 15 min
- Estimated sleep time
- 7h 45m
- Estimated 90-min cycles
- 5.2 cycles
Recommended sleep by age
| Age group | Hours per day |
|---|---|
| Newborn (0–3 mo) | 14 – 17 |
| Infant (4–11 mo) | 12 – 15 |
| Toddler (1–2 yr) | 11 – 14 |
| Preschool (3–5 yr) | 10 – 13 |
| School age (6–13 yr) | 9 – 11 |
| Teen (14–17 yr) | 8 – 10 |
| Young adult (18–25 yr) | 7 – 9 |
| Adult (26–64 yr) | 7 – 9 |
| Older adult (65+ yr) | 7 – 8 |
Source: National Sleep Foundation sleep-duration guidance. Individual needs may vary.
Tips for better sleep
Keep a consistent schedule
Go to bed and wake up at the same time every day, including weekends, to support your circadian rhythm.
Limit evening caffeine
Avoid caffeine, large meals, and alcohol for 4 to 6 hours before bedtime to reduce night awakenings.
Dim screens before bed
Turn off phones, tablets, and bright screens at least 30 to 60 minutes before you plan to sleep.
Create a restful room
Keep your bedroom dark, quiet, and comfortably cool (around 65°F / 18°C) for deeper rest.
Source: NHLBI healthy sleep habits. Adapt these general tips to your schedule.
Sleep is the best meditation.— Dalai Lama
Sleep Hours, Bedtimes and Wake-Up Times
Toolslight’s sleep calculator lets you plan when to sleep based on 90-minute sleep cycles, or calculate exact sleep duration between any bedtime and wake-up time. Already know both times? Select “Hours of sleep…” in the calculator above to measure your time in bed, estimated sleep, and cycle counts with customizable fall-asleep buffers.
How Many Hours of Sleep Will I Get?
To work out your sleep duration, count the time from bedtime to waking, including the hours on both sides of midnight. For example, 11pm to 7am is 8 hours, while 11pm to 6am is 7 hours, and 10pm to 5am is 7 hours. These are clock-time intervals in bed, not measurements of how long you actually sleep.
If bedtime means getting into bed, subtract the time you take to fall asleep (sleep latency) and any time spent awake during the night. Eight hours in bed becomes an estimated 7 hours 45 minutes asleep with the standard 15-minute fall-asleep allowance.
The table below lists common bedtime and alarm combinations ending the following morning (assuming no daylight saving clock changes). “Estimated time asleep” allows 15 minutes to fall asleep and assumes no overnight waking. Shorter durations are mathematical arithmetic, not recommended sleep targets.
| Bedtime to wake-up | Time in bed | Estimated time asleep (15-min allowance) |
|---|---|---|
| 11pm to 7am 23:00 to 07:00 | 8 hours | 7h 45m |
| 10pm to 5am 22:00 to 05:00 | 7 hours | 6h 45m |
| 11pm to 6am 23:00 to 06:00 | 7 hours | 6h 45m |
| 9pm to 5am 21:00 to 05:00 | 8 hours | 7h 45m |
| 10pm to 6am 22:00 to 06:00 | 8 hours | 7h 45m |
| 9pm to 6am 21:00 to 06:00 | 9 hours | 8h 45m |
| 11pm to 5am 23:00 to 05:00 | 6 hours | 5h 45m |
| 12am (midnight) to 7am 00:00 to 07:00 | 7 hours | 6h 45m |
| 1am to 7am 01:00 to 07:00 | 6 hours | 5h 45m |
| 10pm to 7am 22:00 to 07:00 | 9 hours | 8h 45m |
| 1am to 8am 01:00 to 08:00 | 7 hours | 6h 45m |
| 9pm to 4am 21:00 to 04:00 | 7 hours | 6h 45m |
| 10pm to 5:30am 22:00 to 05:30 | 7 hours 30m | 7h 15m |
| 11pm to 8am 23:00 to 08:00 | 9 hours | 8h 45m |
If I Sleep Now and Wake Up at 5am, How Many Hours Will I Get?
Count from your current local time to the next 5:00 AM. If it is 10:00 PM now, you have 7 hours in bed; at 11:00 PM, you have 6 hours. Subtract your fall-asleep buffer and any overnight waking to estimate time asleep. If 5:00 AM has already passed today, count toward tomorrow morning.
To calculate the exact hours remaining right now, choose “Hours of sleep…” in the calculator, set the bedtime to your current clock, and select 5:00 AM as your wake-up time. To plan an earlier bedtime around a fixed 5:00 AM alarm instead, choose “Wake up at…” and select 5:00 AM.
How to Use the Bedtime, Wake-Up and Sleep Duration Calculator
- Choose your mode: Select “Hours of sleep…” to measure duration between two times, “Wake up at…” to find bedtimes for an alarm, or “Sleep at…” to find wake-up times from when you sleep.
- Set your time: Tap the hour or minute, use the stepper arrows, or pick a quick minute preset (:00, :15, :30, :45). Check AM/PM in 12-hour mode or switch to 24-hour mode.
- Adjust sleep settings: Open “Sleep settings” to customize your time to fall asleep (default 15 minutes) or assumed cycle length (default 90 minutes).
- Calculate and save: Click Find bedtimes or Calculate sleep hours to view your schedule breakdown, cycle metrics, and age guidelines. Use Copy summary to copy your results.
Going to bed right now? Click the “Sleep now” shortcut to calculate immediate cycle wake-up targets from your device’s current clock.
How the Sleep Cycle Estimate Works
The cycle calculator model starts with an assumed 90-minute sleep cycle length and adds a configurable allowance for falling asleep. To estimate bedtime, it subtracts both from your target wake-up time. To estimate wake-up times, it adds them to your planned bedtime.
- Bedtime = wake-up time − (cycles × cycle length) − time to fall asleep.
- Wake-up time = bedtime + time to fall asleep + (cycles × cycle length).
For example, five assumed 90-minute cycles equal 450 minutes, or 7 hours 30 minutes asleep, requiring 7 hours 45 minutes in bed with the default 15-minute allowance.
Actual sleep cycles vary between individuals and across the night. The US National Heart, Lung, and Blood Institute (NHLBI) notes that adult cycles generally last between 80 and 100 minutes. The CDC recommends at least seven hours of sleep per night for adults aged 18–60. Use these estimates as helpful planning guidelines rather than clinical measurements of sleep stages.
Bedtime Examples for Common Wake-Up Times
These examples allow 15 minutes to fall asleep and assume no nighttime awakenings. Bedtimes for 7.5 hours (5 cycles), 8 hours (standard full rest), and 9 hours (6 cycles) are displayed in both 12-hour and 24-hour formats.
| Wake-up time | Bedtime for 7.5h asleep (5 cycles) |
Bedtime for 8 hours asleep |
Bedtime for 9h asleep (6 cycles) |
|---|---|---|---|
| 5:00 AM 05:00 |
9:15 PM 21:15 |
8:45 PM 20:45 |
7:45 PM 19:45 |
| 6:00 AM 06:00 |
10:15 PM 22:15 |
9:45 PM 21:45 |
8:45 PM 20:45 |
| 6:30 AM 06:30 |
10:45 PM 22:45 |
10:15 PM 22:15 |
9:15 PM 21:15 |
| 7:00 AM 07:00 |
11:15 PM 23:15 |
10:45 PM 22:45 |
9:45 PM 21:45 |
| 8:00 AM 08:00 |
12:15 AM 00:15 |
11:45 PM 23:45 |
10:45 PM 22:45 |
Frequently Asked Questions FAQs
How does this sleep calculator work?
It estimates bedtimes or wake-up times using your selected time, an assumed sleep-cycle length and a buffer for falling asleep. The defaults are 90-minute cycles and a 15-minute buffer. You can also select “Hours of sleep” to calculate exact time in bed, estimated sleep, and cycle counts between any two specific times.
How many hours of sleep is 11pm to 7am?
11:00 PM to 7:00 AM the following morning is 8 hours. If you get into bed at 11:00 PM and take 15 minutes to fall asleep, that leaves an estimated 7 hours 45 minutes asleep (about 5.2 ninety-minute cycles), assuming no overnight waking. Any time spent awake reduces the total.
If I sleep at 11pm and wake up at 6am, how many hours is that?
11:00 PM to 6:00 AM the following morning is 7 hours. If 11:00 PM is when you get into bed, subtract the time you take to fall asleep. With a 15-minute allowance and no overnight waking, the estimated sleep duration is 6 hours 45 minutes (about 4.5 ninety-minute cycles).
If I sleep at 10pm and wake up at 5am, how many hours is that?
10:00 PM to 5:00 AM the following morning is 7 hours. If you are asleep for that entire period, that is seven hours asleep. If you get into bed at 10:00 PM and take 15 minutes to fall asleep, it allows an estimated 6 hours 45 minutes asleep before any overnight waking.
If I sleep at 9pm and wake up at 5am, how many hours is that?
9:00 PM to 5:00 AM the following morning is 8 hours. If you get into bed at 9:00 PM and fall asleep 15 minutes later, that allows an estimated 7 hours 45 minutes asleep. Time spent awake during the night reduces that estimate further.
How many hours of sleep is 10pm to 6am?
10:00 PM to 6:00 AM the following morning is 8 hours. If you get into bed at 10:00 PM and take 15 minutes to fall asleep, that allows an estimated 7 hours 45 minutes asleep. Subtract any time spent awake during the night from that estimate.
How many hours of sleep is 9pm to 6am?
9:00 PM to 6:00 AM the following morning is 9 hours. With a 15-minute allowance for falling asleep, the estimated sleep duration is 8 hours 45 minutes, assuming no overnight waking. If 9:00 PM is when you actually fell asleep, do not subtract the allowance again.
How many hours of sleep is 11pm to 5am?
11:00 PM to 5:00 AM the following morning is 6 hours. With 15 minutes to fall asleep, that allows an estimated 5 hours 45 minutes asleep before any overnight waking. Six hours is below the CDC recommendation of at least seven hours for adults aged 18–60.
If I sleep now and wake up at 5am, how many hours will I get?
Count from your current local time to the next 5:00 AM. At 10:00 PM, that is 7 hours in bed, or 6 hours 45 minutes asleep after a 15-minute fall-asleep buffer. To calculate your exact remaining hours right now, select “Hours of sleep” in the calculator above and set 5:00 AM as your wake-up time.
How many hours of sleep is 12am to 7am?
12:00 AM (midnight) to 7:00 AM is 7 hours. If midnight is your bedtime and you take 15 minutes to fall asleep, that leaves an estimated 6 hours 45 minutes asleep before overnight waking. Here, 12:00 AM means midnight; 12:00 PM means noon and describes a different daytime interval.
If I sleep at 1am and wake up at 7am, how many hours is that?
1:00 AM to 7:00 AM is 6 hours. If you get into bed at 1:00 AM and take 15 minutes to fall asleep, that allows an estimated 5 hours 45 minutes asleep before any overnight waking. This is below the CDC’s recommended 7-hour minimum for adults.
How many hours of sleep is 10pm to 7am?
10:00 PM to 7:00 AM the following morning is 9 hours. If you go to bed at 10:00 PM and fall asleep 15 minutes later, you spend an estimated 8 hours 45 minutes asleep. Any time awake during the night reduces that total; the calculator cannot measure those awakenings.
How do I calculate sleep hours if I wake up during the night?
Add the time you were asleep in each separate period, or subtract total awake time from your full bedtime-to-waking interval. For example, 11:00 PM to 7:00 AM is 8 hours in bed. Subtracting 15 minutes to fall asleep and 30 minutes awake leaves 7 hours 15 minutes of actual sleep.
If I sleep at 1am and wake up at 8am, how many hours is that?
1:00 AM to 8:00 AM is 7 hours. If 1:00 AM is when you get into bed and you take 15 minutes to fall asleep, the estimated sleep duration is 6 hours 45 minutes. Subtract any overnight waking as well. If you were already asleep at 1:00 AM, omit the fall-asleep deduction.
How many hours of sleep is 9pm to 4am?
9:00 PM to 4:00 AM the following morning is 7 hours. If you take 15 minutes to fall asleep after getting into bed at 9:00 PM, that leaves an estimated 6 hours 45 minutes asleep. Count three hours before midnight and four hours after it, then subtract any awake time.
If I sleep now, what time should I wake up?
Select “Sleep now” in the calculator to estimate possible wake-up times from your device’s current clock. With the default 15-minute buffer, the 7.5-hour and 9-hour options are 7 hours 45 minutes and 9 hours 15 minutes from now. Choose a target that fits your morning commitments.
What time should I go to bed to wake up at 6am?
With a 15-minute fall-asleep buffer, go to bed at 10:15 PM for an estimated 7.5 hours asleep (5 cycles), 9:45 PM for 8 hours asleep, or 8:45 PM for 9 hours asleep (6 cycles). These are default estimates for a 6:00 AM alarm.
What time should I go to bed to wake up at 6:30am?
For a 6:30 AM wake-up, the default estimates are 10:45 PM for 7.5 hours asleep (5 cycles), 10:15 PM for 8 hours asleep, or 9:15 PM for 9 hours asleep. Both allow 15 minutes to fall asleep.
What time should I go to bed to wake up at 7am?
For a 7:00 AM wake-up, go to bed at 11:15 PM for an estimated 7.5 hours asleep (5 cycles), 10:45 PM for 8 hours asleep, or 9:45 PM for 9 hours asleep. If you need longer to fall asleep, adjust the buffer in settings.
What time should I go to bed to wake up at 8am?
For an 8:00 AM wake-up, the default estimates are 12:15 AM for 7.5 hours asleep, 11:45 PM the previous evening for 8 hours asleep, or 10:45 PM for 9 hours. All include a 15-minute fall-asleep buffer.
What time should I go to bed to wake up at 5am?
With the default 15-minute buffer, go to bed at 9:15 PM for an estimated 7.5 hours asleep, 8:45 PM for 8 hours asleep, or 7:45 PM for 9 hours asleep. These are previous-evening bedtimes for a 5:00 AM wake-up.
What time should I wake up if I go to bed at 11pm?
If you get into bed at 11:00 PM and take 15 minutes to fall asleep, 6:45 AM allows an estimated 7.5 hours asleep (5 cycles), 7:15 AM gives 8 hours, and 8:15 AM allows 9 hours. Getting into bed and falling asleep are different times; the buffer accounts for that difference.
What time should I wake up if I go to bed at midnight?
If you get into bed at 12:00 AM and fall asleep around 12:15 AM, the default estimates are 7:45 AM for 7.5 hours asleep (5 cycles), 8:15 AM for 8 hours asleep, or 9:15 AM for 9 hours asleep.
Can a sleep cycle calculator predict REM or light sleep?
No. Cycle calculators estimate schedules from mathematical assumptions. Eight hours divided by 90 minutes is about 5.33, but that does not measure your actual brainwaves or identify your waking stage. The NHLBI explains how sleep cycles vary between 80 and 100 minutes.
Does the calculator include time to fall asleep?
Yes. The default buffer is 15 minutes, and you can customize it from 0 to 120 minutes in the settings. The time between getting into bed and falling asleep is known as sleep latency.
Is six hours of sleep enough for adults?
Six hours is below the CDC’s recommendation of at least seven hours for adults aged 18–60. A shorter duration appearing in arithmetic results does not make it an adequate regular sleep target. Prioritize enough total sleep rather than a specific cycle count.
Why do I feel tired after eight hours of sleep?
Total time asleep is only part of restorative rest. Sleep quality, sleep apnea, circadian misalignment, and frequent nighttime awakenings can all cause morning fatigue. The CDC notes that persistent daytime exhaustion despite adequate hours warrants medical consultation.
Can I use this sleep calculator in the UK or US with a 24-hour clock?
Yes. Enter your bedtime or wake-up time in your local time and toggle between the 12-hour (AM/PM) and 24-hour display in the settings. The “Sleep now” option automatically reads your device’s current clock and time zone.
Related Planning Tools
- Need to measure work shifts, break deductions, or a time span not listed above? Use the Hours Between Two Times Calculator (set break deductions to zero to see total elapsed time in bed).
- Taking a nap or timing an exact sleep duration starting right now? Find your target finish time with the Hours From Now Calculator.
- Converting sleep cycle lengths (such as 450 minutes for 5 cycles) into decimal hours and formatted time? Check out the Minutes to Hours Converter.