Sleep Calculator
Find a bedtime or wake up time that fits whole sleep cycles and meets the recommended hours of sleep for your age.
Going to sleep now, at โ.
Advanced options
Meets the CDC recommendation of 7 or more hours for adults aged 18 to 60.
15 min to fall asleep, then 5 sleep cycles of 90 min each.
Other bedtimes
For a 6:30 AM wake up. Each time puts the alarm at the end of a cycle.
- 9:15 PM6 cycles, 9 h of sleepMeets 7+ h
- 12:15 AM4 cycles, 6 h of sleepBelow 7 h
- 1:45 AM3 cycles, 4 h 30 min of sleepBelow 7 h
Your calculation
The same steps the calculator runs, with your times.
- Sleep: 5 cycles ร 90 min = 450 min = 7 h 30 min.
- Fall asleep by: 6:30 AM โ 7 h 30 min = 11:00 PM.
- Bedtime: 11:00 PM โ 15 min to fall asleep = 10:45 PM.
- Check: 7 h 30 min meets the CDC recommendation of 7 or more hours for adults aged 18 to 60.
Recommended sleep by age
CDC daily recommendations. Your group is highlighted.
| Age group | Age | Sleep per day |
|---|---|---|
| Newborn | 0 to 3 months | 14 to 17 hours |
| Infant | 4 to 12 months | 12 to 16 hours, including naps |
| Toddler | 1 to 2 years | 11 to 14 hours, including naps |
| Preschool | 3 to 5 years | 10 to 13 hours, including naps |
| School age | 6 to 12 years | 9 to 12 hours |
| Teen | 13 to 17 years | 8 to 10 hours |
| Adult | 18 to 60 years | 7 or more hours |
| Adult | 61 to 64 years | 7 to 9 hours |
| Adult | 65 years and older | 7 to 8 hours |
Sleep cycles vary from about 80 to 100 minutes between people and through the night, so treat these times as a planning guide, not a medical recommendation.
How the Sleep Calculator Works
This sleep calculator answers two everyday questions: what time should I go to bed to wake up at a set time, and what time should I wake up if I go to bed now or at a set time. It counts backward or forward in whole sleep cycles, adds the time you take to fall asleep, and checks each result against the hours of sleep the CDC recommends for your age group.
Sleep runs in repeating cycles of non REM and REM sleep. The National Heart, Lung, and Blood Institute (NHLBI) describes each cycle as lasting 80 to 100 minutes, with four to six cycles in a typical night, and notes that you may wake briefly between cycles. The calculator uses 90 minutes by default and places each suggested time at the end of a cycle.
Working forward is the same arithmetic in reverse. In bed at 11:30 PM and asleep 15 minutes later at 11:45 PM, five cycles end at 7:15 AM and six cycles end at 8:45 AM.
How Much Sleep Do You Need by Age?
The CDC publishes recommended daily sleep by age, drawn from consensus statements by the American Academy of Sleep Medicine and the National Sleep Foundation. The table in the results lists every group. The key adult figure is 7 or more hours a night for ages 18 to 60, narrowing to 7 to 9 hours at 61 to 64 and 7 to 8 hours at 65 and older.
Teens aged 13 to 17 need 8 to 10 hours and children aged 6 to 12 need 9 to 12 hours. For children under 6, the recommendation is a daily total that includes naps, such as 10 to 13 hours at ages 3 to 5. A single overnight bedtime cannot capture nap schedules, so this calculator covers ages 6 and up and lists younger groups for reference.
The National Institute of Neurological Disorders and Stroke (NINDS) points out that sleep need varies widely between people of the same age, and that no single amount works for everybody. The recommendations are ranges for that reason. If you regularly feel sleepy after getting the recommended hours, the CDC advises talking to a healthcare provider.
How the calculator picks the main time
For each age group the calculator chooses the number of cycles whose total sleep falls inside the recommended range and sits closest to its middle. For adults 18 to 60, whose range has no upper limit, it aims for 8 hours. With 90 minute cycles that gives 5 cycles (7 h 30 min) for adults, 6 cycles (9 h) for teens and 7 cycles (10 h 30 min) for children aged 6 to 12.
Bedtime Chart by Wake Up Time
Bedtimes for common wake up times, with 90 minute cycles and 15 minutes to fall asleep. Six cycles give 9 hours of sleep, five give 7 hours 30 minutes and four give 6 hours.
| Wake up at | 6 cycles (9 h) | 5 cycles (7 h 30 min) | 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 |
Wake up times by bedtime
| In bed at | 4 cycles | 5 cycles | 6 cycles |
|---|---|---|---|
| 9:00 PM | 3:15 AM | 4:45 AM | 6:15 AM |
| 10:00 PM | 4:15 AM | 5:45 AM | 7:15 AM |
| 10:30 PM | 4:45 AM | 6:15 AM | 7:45 AM |
| 11:00 PM | 5:15 AM | 6:45 AM | 8:15 AM |
| 11:30 PM | 5:45 AM | 7:15 AM | 8:45 AM |
| 12:00 AM | 6:15 AM | 7:45 AM | 9:15 AM |
Sleep Cycles and Sleep Stages
NINDS describes two types of sleep: non REM sleep, which has three stages, and REM sleep. Each cycle passes through them in order, and the mix changes as the night goes on.
- Stage 1 non REM is the changeover from waking to sleep and usually lasts several minutes.
- Stage 2 non REM is light sleep. Heart rate and breathing slow and body temperature drops. You spend more of your cycles in stage 2 than in any other stage.
- Stage 3 non REM is deep sleep, the stage you need to feel refreshed. It comes in longer periods during the first half of the night.
- REM sleep first occurs about 90 minutes after falling asleep. Most dreaming happens here, and REM periods grow longer later in the night.
Because deep sleep is concentrated early and REM periods are longer late, an early alarm mainly shortens the later cycles, which hold the longer REM periods. Cycle length differs between people and between cycles of the same night, which is why the calculator lets you set your own length from 60 to 120 minutes.
How to Use the Calculator
- Pick a mode. Choose Wake up at to get bedtimes, Go to bed at to get wake up times, or Sleep now to count from the current time on your device.
- Enter the time. Use the time box in Wake up at and Go to bed at modes.
- Choose your age group. It sets the recommended hours used to pick the main time and to label the others as meeting, below or above the range.
- Set minutes to fall asleep. Enter how long you usually lie awake before sleep. The default is 15 minutes.
- Adjust the cycle length if you know it. Open Advanced options to change it, or switch to a 24 hour clock.
The large time at the top is the suggested bedtime or alarm. The card below lists the other cycle options, and the tiles show the time in bed, when sleep starts or ends, your recommendation and the weekly total.
Common Mistakes
- Counting time in bed as sleep. Lying awake for 20 minutes means a 10:45 PM bedtime starts sleep at 11:05 PM, not 10:45 PM.
- Treating 90 minutes as exact. Cycles run 80 to 100 minutes, so five cycles can last from 6 h 40 min to 8 h 20 min.
- Using adult hours for a teen. Five cycles meet the adult minimum of 7 hours but fall short of the teen range of 8 to 10.
- Choosing cycles over total sleep. Four cycles end neatly but give only 6 hours with 90 minute cycles.
- Shifting the schedule on weekends. The CDC lists a consistent bed and wake time every day as a habit that improves sleep.
Habits That Support Better Sleep
The CDC lists these habits for better sleep:
- Go to bed and get up at the same time every day.
- Keep the bedroom quiet, relaxing and cool.
- Turn off electronic devices at least 30 minutes before bedtime.
- Avoid large meals and alcohol before bedtime.
- Avoid caffeine in the afternoon or evening.
- Exercise regularly and eat a healthy diet.
Frequently Asked Questions
What time should I go to bed if I wake up at 6 AM?
Go to bed at 10:15 PM for five sleep cycles, or 8:45 PM for six. Both times assume cycles of 90 minutes and about 15 minutes to fall asleep. Five cycles give 7 hours 30 minutes of sleep, which meets the CDC recommendation of 7 or more hours for adults aged 18 to 60. Six cycles give 9 hours, which suits teens, whose recommendation is 8 to 10 hours. A bedtime of 11:45 PM gives only four cycles, or 6 hours, which is below the adult recommendation.
What time should I wake up if I go to bed at 11 PM?
Wake up at 6:45 AM for five sleep cycles, or 8:15 AM for six. If you fall asleep in about 15 minutes, you are asleep by 11:15 PM, and each cycle adds 90 minutes. Five cycles give 7 hours 30 minutes of sleep and six give 9 hours. Waking at 5:15 AM gives four cycles, or 6 hours, which is below the 7 hours the CDC recommends for adults. Change the minutes to fall asleep or the cycle length in this calculator if your nights differ.
How many hours of sleep do I need?
The CDC recommends 7 or more hours a night for adults aged 18 to 60, 7 to 9 hours for ages 61 to 64 and 7 to 8 hours for 65 and older. Teens aged 13 to 17 need 8 to 10 hours and children aged 6 to 12 need 9 to 12 hours. Younger children need more, counted per day including naps: 10 to 13 hours at ages 3 to 5, 11 to 14 hours at ages 1 to 2 and 12 to 16 hours for infants aged 4 to 12 months.
How long is a sleep cycle?
A sleep cycle lasts about 80 to 100 minutes, according to the National Heart, Lung, and Blood Institute, and most people complete four to six cycles a night. Each cycle moves through three stages of non REM sleep and then REM sleep, and you may wake briefly between cycles. Deep sleep fills more of the early cycles and REM periods grow longer toward morning. This calculator uses 90 minutes by default, the middle of that range, and lets you set any length from 60 to 120 minutes.
How much sleep do teenagers need?
Teens aged 13 to 17 need 8 to 10 hours of sleep a night, according to the CDC, based on the American Academy of Sleep Medicine pediatric consensus statement. With 90 minute cycles, six cycles give 9 hours, the middle of that range. A teen who must wake at 6:30 AM and takes about 15 minutes to fall asleep needs to be in bed by 9:15 PM for six cycles. Five cycles, or 7 hours 30 minutes, fall below the teen recommendation even though they meet the adult one.
Can you catch up on sleep on the weekend?
Only partly. The National Institute of Neurological Disorders and Stroke notes that sleeping longer on weekends may not be enough to replace the sleep missed during the week, depending on how sleep deprived you are. The CDC lists going to bed and getting up at the same time every day as a habit that improves sleep. Sleeping 6 hours a night for five work nights instead of 7 hours 30 minutes leaves a deficit of 7 hours 30 minutes, a full night of sleep.
Sources & References
- Centers for Disease Control and Prevention. About Sleep (recommended hours of sleep by age, sleep habits, sleep quality), May 15, 2024. cdc.gov
- National Heart, Lung, and Blood Institute. How Sleep Works: Sleep Phases and Stages (cycles of 80 to 100 minutes, four to six per night), updated March 24, 2022. nhlbi.nih.gov
- National Institute of Neurological Disorders and Stroke. Brain Basics: Understanding Sleep (sleep stages, first REM about 90 minutes after falling asleep, weekend catch up), reviewed February 25, 2025. ninds.nih.gov
- Watson NF, Badr MS, et al. Recommended Amount of Sleep for a Healthy Adult: A Joint Consensus Statement of the AASM and Sleep Research Society. Sleep, 2015. pubmed.ncbi.nlm.nih.gov
- Paruthi S, Brooks LJ, et al. Recommended Amount of Sleep for Pediatric Populations: A Consensus Statement of the AASM. J Clin Sleep Med, 2016. pubmed.ncbi.nlm.nih.gov
Results are for informational purposes only and should not be used as a diagnosis or substitute for professional medical advice. Every time on this page was recomputed with the same code the calculator uses. Methodology reviewed: 2026.