What Time Should I Go to Bed? Sleep Cycles Explained
The short answer
Count back from the time you have to get up. Take off the time it takes you to fall asleep, then the hours of sleep you need. For most adults the CDC recommends 7 or more hours, so if you wake at 6:30 am and take about 15 minutes to drop off, a bedtime of 10:45 pm gives you 7½ hours of sleep, which is five 90-minute cycles.
The cycle part is a refinement, not a rule. Sleep does run in repeating cycles, but their length varies from person to person and through the night. Getting enough total sleep matters more than landing exactly on a cycle boundary. The sleep calculator does the counting for any wake-up time or bedtime.
How much sleep you need, by age
The CDC’s About Sleep page gives these recommendations, drawn from American Academy of Sleep Medicine (AASM) consensus statements and the National Sleep Foundation:
| Age | Recommended sleep per day |
|---|---|
| 0 to 3 months | 14 to 17 hours |
| 4 to 12 months | 12 to 16 hours, including naps |
| 1 to 2 years | 11 to 14 hours, including naps |
| 3 to 5 years | 10 to 13 hours, including naps |
| 6 to 12 years | 9 to 12 hours |
| 13 to 17 years | 8 to 10 hours |
| 18 to 60 years | 7 or more hours |
| 61 to 64 years | 7 to 9 hours |
| 65 and older | 7 to 8 hours |
The AASM and Sleep Research Society agreed that 7 or more hours a night is recommended for all healthy adults, and said that sleeping six or fewer hours is inadequate to sustain health and safety. They set no upper limit, noting that more than nine hours a night may be appropriate for young adults, people recovering from sleep debt and people who are ill.
What a sleep cycle is
The National Institute of Neurological Disorders and Stroke (NINDS) describes two basic types of sleep in its Brain Basics guide: non-REM sleep, which has three stages, and REM sleep, when most dreaming happens.
- Stage 1 is the short changeover from waking to sleep, usually lasting several minutes.
- Stage 2 is light sleep. NINDS says you spend more of your repeated cycles in stage 2 than in any other stage.
- Stage 3 is deep sleep, the stage you need to feel refreshed in the morning. It comes in longer periods during the first half of the night.
- REM sleep first occurs about 90 minutes after you fall asleep.
You cycle through non-REM and REM sleep several times a night, with REM periods growing longer and deeper later on. The 90-minute step that sleep calculators use lines up with that first REM period. Real cycles are not a fixed length, and the mix inside them shifts across the night.
Bedtimes by wake-up time
These bedtimes allow 15 minutes to fall asleep and use 90-minute cycles. Six cycles is 9 hours of sleep, five is 7½ hours and four is 6 hours.
| Wake up at | 6 cycles (9 h) | 5 cycles (7½ h) | 4 cycles (6 h) |
|---|---|---|---|
| 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 |
How to read it by age:
- Adults 18 to 60: five or six cycles both meet the 7-hour minimum. The 6-hour column does not.
- Teens 13 to 17: only the 9-hour column falls inside the CDC’s 8 to 10 hours. Five cycles, at 7½ hours, is short.
- Children 6 to 12: 9 hours is the bottom of their 9 to 12 hour range, so the 6-cycle bedtime is the latest that works, and earlier is better.
Worked example: a 6:30 am alarm
You need to be up at 6:30 am and usually fall asleep in about 15 minutes.
- Take off the time to fall asleep: 6:30 am − 15 minutes = asleep by 6:15 am.
- Five cycles is 5 × 90 = 450 minutes, or 7 hours 30 minutes.
- 6:15 am − 7:30 = 10:45 pm.
For an adult that is the latest of the cycle-based bedtimes that still gives 7 or more hours. A 12:15 am bedtime would also end on a cycle, but at 6 hours it falls short of the CDC’s recommendation. A teenager with the same alarm should aim for 9:15 pm.
How long it takes to fall asleep
The 15 minutes in these tables is an adjustable assumption. The Sleep Foundation’s guide to sleep latency says a healthy person takes on average 10 to 20 minutes to fall asleep. It also says that falling asleep in under 8 minutes can be a sign of increased sleepiness, and that regularly taking much longer than 20 to 30 minutes may point to insomnia or another sleep problem.
If you know you take 30 minutes, move every bedtime in the table 15 minutes earlier. The sleep calculator lets you set your own time to fall asleep and your own cycle length.
What cycle timing can and cannot do
The idea. Cycle-based bedtimes aim to have you wake near the end of a cycle, in lighter sleep, rather than be pulled out of deep sleep. NINDS notes that deep sleep comes in longer periods during the first half of the night, so the morning end of the night holds less of it.
What it cannot do. It cannot make a short night long enough. Six hours that ends neatly on a cycle is still under the 7 hours recommended for adults. It also cannot predict your cycles exactly: NINDS notes that sleep patterns vary significantly between people of the same age.
So use the 90-minute steps to choose between bedtimes that already give you enough sleep, not to justify less of it.
Habits that make the bedtime work
The CDC suggests 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 bed.
- Avoid large meals and alcohol before bedtime.
- Avoid caffeine in the afternoon or evening.
- Exercise regularly and keep a healthy diet.
NINDS adds that if you cannot get to sleep, it helps to get up and do something relaxing until you feel tired, rather than lying in bed awake. Both the CDC and NINDS advise seeing a doctor about ongoing sleep problems or unusual tiredness during the day.
Related tools
- Sleep calculator: bedtimes or wake-up times for your age, time to fall asleep and cycle length.
- Workout plan generator: a printable weekly plan, for the regular exercise both the CDC and NINDS mention.
- Steps to miles calculator: turn a daily walk into miles.
Recommendations on this page were checked against the CDC, AASM, NINDS and Sleep Foundation pages in October 2026. This page is general information, not medical advice.