Sleep Calculator
Find out when to go to bed or wake up so you finish a full sleep cycle, and see a REM and non-REM sleep-stage graph for that night.
We will tell you when to go to bed to wake up at this time.
We will tell you when to wake up feeling rested if you go to bed at this time.
Using the time you press the button, we will tell you when to wake up feeling rested.
Each option is marked against the sleep duration recommended for your age group (National Sleep Foundation).
Advanced · adjust to your body
The average is 90 minutes, but it ranges from about 80 to 100 between people.
How long it takes you to actually fall asleep after lying down. Usually 10–20 minutes.
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Time to fall asleep is already included. Tap an option to change that night’s sleep-stage graph.
- Awake
- REM sleep
- Light sleep N1
- Light sleep N2
- Deep sleep N3
※ The graph and stage times are estimates based on the average adult sleep structure. Only an overnight sleep study (polysomnography) can show your real sleep stages. If you stay tired after sleeping or suspect a sleep disorder, see a doctor.
How to use
Recommended sleep by age group
| Age group | Recommended sleep per day |
|---|---|
| Toddler (1–2) | 11–14 hours |
| Preschool (3–5) | 10–13 hours |
| School age (6–13) | 9–11 hours |
| Teen (14–17) | 8–10 hours |
| Young adult (18–25) | 7–9 hours |
| Adult (26–64) | 7–9 hours |
| Older adult (65+) | 7–8 hours |
Source: National Sleep Foundation recommendations. Individual needs vary, so use them as a guide. For children age 5 and under the sleep cycle is shorter (about 50–60 minutes), so this calculator is not designed for them.
How the sleep calculator works
This sleep calculator works backward or forward from the time you choose to suggest bedtimes and wake-up times that line up with the end of a sleep cycle. Enter the time you need to get up, and it lists times to fall asleep. Enter the time you plan to go to bed, or just tap Sleep now, and it lists times to wake up. Each option shows how many cycles it covers and the total sleep it gives you, tagged as recommended, too short or too long for your age group. Tap any option to see a graph of that night’s estimated REM, light and deep sleep.
What is a sleep cycle?
During the night your brain moves through repeating cycles of sleep stages. A cycle starts with light sleep (N1 and N2), drops into deep sleep (N3) and then rises into REM sleep, the stage in which most vivid dreaming happens. The average cycle lasts about 90 minutes, though it can be anywhere from roughly 80 to 100 minutes depending on the person and the night. Most people complete four to six cycles, which equals six to nine hours. Deep sleep is concentrated in the first half of the night, and REM periods grow longer toward morning, which is why cutting your night short usually costs you REM sleep.
Why time your sleep around cycles?
Waking in the middle of deep sleep often leaves you foggy and groggy, a feeling called sleep inertia. Waking near the end of a cycle, when sleep is lighter, tends to feel easier. The calculator therefore suggests times that are a whole number of cycles plus the time it takes you to fall asleep. It is a useful planning aid, not a promise: cycle length varies, alarms interrupt at random points, and total sleep matters more than the exact minute you wake up.
Bedtime = wake-up time − (cycles × cycle length) − time to fall asleep
For example, if you must be up at 6:30 AM and you need about 15 minutes to fall asleep, then five 90-minute cycles (7 hours 30 minutes) mean getting into bed at 10:45 PM. Six cycles (9 hours) mean 9:15 PM, and four cycles (6 hours) mean 12:15 AM.
How much sleep do you need?
The National Sleep Foundation recommends 7 to 9 hours for adults aged 18 to 64, and 7 to 8 hours for adults 65 and older. Teens aged 14 to 17 need 8 to 10 hours, school-age children 9 to 11, preschoolers 10 to 13 and toddlers 11 to 14. The American Academy of Sleep Medicine and the Sleep Research Society have likewise said that adults should regularly sleep seven or more hours a night for good health. Some people function well at the lower end of the range and others need the upper end; what matters is how you feel and perform during the day. The table on this page lists all the age groups for quick reference.
Fall-asleep time and cycle length settings
The Advanced settings let you adjust the two numbers that vary most between people. If you usually fall asleep within five minutes, choose 5; if you often lie awake for half an hour, choose 30, and the suggested bedtimes shift earlier. If you know you wake naturally after about 80 or 100 minutes, change the cycle length. A reliable way to find your own numbers is to keep a sleep diary for two weeks, noting when you go to bed and wake up and how you feel.
Habits that make the calculator work better
- Keep a consistent schedule. Going to bed and waking at about the same times every day, including weekends, trains your body clock and makes your estimated cycle times more accurate.
- Watch caffeine timing. Caffeine has a half-life of roughly five to six hours, so an afternoon coffee can still be affecting you at bedtime. Many sleep specialists suggest stopping caffeine at least six to eight hours before bed.
- Dim the lights and screens. Bright light in the last hour before bed can delay your internal clock. A cool, dark, quiet room helps you fall asleep faster.
- Mind alcohol. It can make you drowsy but fragments sleep later in the night and reduces REM sleep.
- Naps. A 20-minute nap or a full 90-minute nap (one full cycle) is less likely to leave you groggy than a 40-to-60-minute nap.
When to talk to a doctor
If you consistently sleep enough but still feel exhausted, snore loudly, stop breathing during sleep, have trouble falling asleep three or more nights a week for a month or longer, or fall asleep at unsafe times, talk to a doctor. Conditions such as sleep apnea, insomnia and restless legs syndrome are common and treatable. The stage graph on this page is an estimate from average adult patterns, and only a sleep study can measure your actual stages.
Frequently asked questions
How long is a sleep cycle?
About 90 minutes on average, with a normal range of roughly 80 to 100 minutes. The first cycles contain more deep sleep, and later cycles contain more REM sleep.
What time should I go to bed if I wake up at 6 AM?
If you fall asleep in about 15 minutes, going to bed at 10:15 PM gives you five full cycles (7.5 hours) and 8:45 PM gives six. Enter 6:00 AM as your wake-up time and the calculator lists each option with the total sleep it provides.
Is five cycles enough?
Five 90-minute cycles equal 7.5 hours, which is inside the recommended range for most adults. Four cycles (6 hours) is below it for most people, though some feel fine on it occasionally. Over time, regularly sleeping less than seven hours is linked with higher health risks.
What does the “Sleep now” option do?
It takes the current time, adds the time you need to fall asleep, and shows times that line up with the end of later cycles, so you can set an alarm if you head to bed right now.
Are the sleep-stage graphs accurate?
They are estimates built from average adult sleep structure: more deep sleep early, more REM later. Your own pattern will differ, and a sleep tracker or sleep study would be needed to see it.
Do teenagers and older adults need different amounts?
Yes. Teens need about 8 to 10 hours and adults 65 and over about 7 to 8, according to the National Sleep Foundation. Choose the right age group so the recommended tags are accurate.
Can I use the calculator to plan a nap?
Yes, with a small tweak. Choose Sleep now and look at the first options: one cycle is about 90 minutes plus the time to fall asleep. For a short power nap, simply set a 20-minute alarm instead, since you will wake before deep sleep begins.
Is my information saved or shared?
The calculator remembers your last choices in your own browser so you do not have to re-enter them. Nothing is sent to a server.