Sleep calculator
Bedtimes and wake-up times that fit your sleep cycles.
Most people take 10–20 minutes.
Go to bed at
9:15 pm or 10:45 pm
For 9 or 7.5 hours of sleep: 6 or 5 full cycles
Bedtimes that end a cycle when you wake
- 6 cycles · 9 hours of sleep✓9:15 pm
- 5 cycles · 7.5 hours of sleep✓10:45 pm
- 4 cycles · 6 hours of sleep12:15 am
- 3 cycles · 4.5 hours of sleep1:45 am
Recommended sleep by age
- Teenagers (14–17)
- 8–10 hours
- Adults (18–64)
- 7–9 hours
- Older adults (65+)
- 7–8 hours
- School children (6–13)
- 9–11 hours
Sleep runs in cycles of about 90 minutes. Waking at the end of a cycle, rather than in deep sleep, usually feels easier. Cycle length varies from 70 to 120 minutes, so treat the times as a guide. If you often feel tired after enough sleep, talk to a doctor.
Processed in your browser. Nothing is uploaded.
How to find the best time to sleep
- 1
Choose whether you know your wake-up time or your bedtime.
- 2
Enter the time.
- 3
Adjust how long you usually take to fall asleep.
- 4
Pick a time that gives 5 or 6 full sleep cycles.
Sleep in cycles, wake up fresher
During the night, sleep moves through light sleep, deep sleep and dream (REM) sleep in cycles of about 90 minutes. Waking at the end of a cycle usually feels easier than being pulled out of deep sleep by an alarm. The calculator finds bedtimes that line up with your wake-up time, or wake-up times that line up with your bedtime.
A sleep cycle calculator and bedtime calculator: what time should I go to bed, or wake up?
How it’s worked out
- Wake-up time known: bedtime = wake-up time − time to fall asleep − cycles × 90 minutes.
- Bedtime known: wake-up time = bedtime + time to fall asleep + cycles × 90 minutes.
To wake at 6:30 am and fall asleep in 15 minutes, go to bed at 9:15 pm for 6 cycles (9 hours) or 10:45 pm for 5 cycles (7.5 hours). Going to bed at 11:00 pm, the best wake-up times are 6:45 am and 8:15 am.
Most adults do best with 5 or 6 cycles; 4 cycles (6 hours) is fine now and then but too little night after night.
How much sleep you need
| Age | Hours a night |
|---|---|
| School children (6–13) | 9–11 |
| Teenagers (14–17) | 8–10 |
| Adults (18–64) | 7–9 |
| Older adults (65+) | 7–8 |
Better sleep habits
- Keep the same wake-up time every day, including weekends.
- Avoid tea, coffee and cola after mid-afternoon.
- Put screens away 30–60 minutes before bed; keep the room dark and cool.
- A short nap of 20 minutes refreshes without leaving you groggy.
Cycle length varies from 70 to 120 minutes between people, so if the times don’t feel right, shift by 15 minutes. If you’re tired despite enough sleep, snore loudly or stop breathing in your sleep, see a doctor.
Shift workers and travellers can use the time zone converter to plan around jet lag.
Frequently asked questions
What time should I go to bed to wake up at 6:30?
For 6 full cycles (9 hours), at 9:15 pm; for 5 cycles (7.5 hours), at 10:45 pm. Both assume you take 15 minutes to fall asleep.
Why 90-minute cycles?
Sleep moves through light, deep and dream (REM) stages in cycles of about 90 minutes. Waking at the end of a cycle, rather than from deep sleep, usually leaves you less groggy.
How much sleep do adults need?
7 to 9 hours a night for adults aged 18 to 64, and 7 to 8 hours from 65. Teenagers need 8 to 10 hours and school children 9 to 11.
What if I still feel tired?
Cycle length varies from person to person, so try shifting your bedtime by 15 minutes. If you’re often tired after enough sleep, or snore loudly, talk to a doctor.