Sleep Calculator
Enter when you want to wake up, or when you go to bed, to see times that fit whole sleep cycles of about 90 minutes, next to the hours of sleep the CDC recommends for your age.
Use your own number. 15 minutes is only a starting value, and it differs from person to person.
To wake up at 7:00 AM, go to bed at
11:15 PM
That allows 5 sleep cycles of about 90 minutes, 7 h 30 min of sleep after about 15 minutes to fall asleep. The CDC recommends 7 or more hours for adults 18–60 years.
| Wake-up time | 7:00 AM |
|---|---|
| 5 cycles × about 90 minutes | −7 h 30 min |
| Time to fall asleep | −15 min |
| Go to bed at | 11:15 PM |
| If your cycles run 80 to 100 minutes | 10:25 PM to 12:05 AM |
| Bedtime | Cycles | Sleep | CDC range |
|---|---|---|---|
| 9:45 PM | 6 | 9 h | Within |
| 11:15 PM | 5 | 7 h 30 min | Within |
| 12:45 AM | 4 | 6 h | Below |
Cycles are not a fixed length. NIH (NHLBI) puts them at 80 to 100 minutes, so the real end of a cycle can be earlier or later than shown. Treat the times as a rough guide.
This is general information, not medical advice. Talk to a doctor about your own numbers.
How this is calculated
During the night you cycle through non-REM and REM sleep several times. The National Institute of Neurological Disorders and Stroke (NINDS, part of the NIH) says REM sleep first occurs about 90 minutes after falling asleep. The National Heart, Lung, and Blood Institute (NHLBI) says the cycle starts over every 80 to 100 minutes and that there are usually four to six cycles a night.
The calculator counts in cycles of 90 minutes, the middle of that range, and adds the time you need to fall asleep. Example: to wake up at 7:00 AM after 5 cycles (7 hours 30 minutes of sleep) and 15 minutes to fall asleep, go to bed at 11:15 PM.
Real cycles are not all the same length. At 80 to 100 minutes each, 5 cycles can end up to 50 minutes earlier or later than the 90-minute estimate, and the result shows that range. Treat the times as a rough guide.
Why cycles at all: in deep sleep (stage 3 non-REM), NINDS writes, “it may be difficult to awaken you”, and deep sleep comes in longer periods during the first half of the night. NHLBI notes that you may wake up briefly between cycles.
How much sleep you need
The CDC recommends a number of hours, not a number of cycles. Its table is based on recommendations of the American Academy of Sleep Medicine, the Sleep Research Society and the National Sleep Foundation:
| Age group | Age | Recommended |
|---|---|---|
| Newborn | 0–3 months | 14–17 hours |
| Infant | 4–12 months | 12–16 hours (including naps) |
| Toddler | 1–2 years | 11–14 hours (including naps) |
| Preschool | 3–5 years | 10–13 hours (including naps) |
| School age | 6–12 years | 9–12 hours |
| Teen | 13–17 years | 8–10 hours |
| Adult | 18–60 years | 7 or more hours |
| Adult | 61–64 years | 7–9 hours |
| Adult | 65 years and older | 7–8 hours |
Sleep needs vary from person to person (NHLBI). NINDS advises seeing a doctor if you have problems sleeping or feel unusually tired during the day.
Sources
Checked against the sources below on .
- CDC: About Sleep, recommended hours of sleep by age (page dated May 15, 2024)
- NINDS (NIH): Brain Basics: Understanding Sleep, sleep stages and cycles
- NHLBI (NIH): How Sleep Works, Sleep Phases and Stages (cycle length 80 to 100 minutes)
- American Academy of Sleep Medicine: Recommended Amount of Sleep for Pediatric Populations (consensus statement, 2016)
Questions people ask
How long is a sleep cycle?
About 90 minutes on average. NHLBI gives 80 to 100 minutes per cycle, and NINDS says REM sleep first occurs about 90 minutes after falling asleep.
How many sleep cycles do I need?
NHLBI says there are usually four to six cycles a night. The CDC recommends 7 or more hours of sleep for adults 18 to 60; five cycles of 90 minutes, 7 hours 30 minutes, meet that.
What time should I go to bed if I wake up at 6 AM?
With 15 minutes to fall asleep: 10:15 PM for 5 cycles (7 hours 30 minutes of sleep) or 8:45 PM for 6 cycles (9 hours).
How much sleep do teenagers need?
8 to 10 hours per day for ages 13 to 17, according to the CDC, based on the American Academy of Sleep Medicine.
Does the time it takes to fall asleep matter?
It moves every time by the same amount. The calculator starts at 15 minutes; enter your own number if you usually need more or less.