Sleep Calculator: When to Wake Up or Go to Bed
This sleep calculator works out bedtimes and wake-up times that line up with your natural sleep cycles. Each cycle lasts about 90 minutes, and waking at the end of one, rather than in the middle of deep sleep, usually leaves you feeling more alert. Enter the time you need to get up, or the time you are going to bed.
| Go to bed at | Sleep cycles | Hours asleep |
|---|
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Quick answer: To wake up at 7:00 AM, aim to be asleep by 10:00 PM (six cycles, 9 hours) or 11:30 PM (five cycles, 7.5 hours). Go to bed about 15 minutes earlier to allow time to drift off.
How to use the sleep calculator
- Choose Wake up at and enter your alarm time to see when to go to bed, or choose Go to bed at to see when to set your alarm.
- Click I’m going to bed now for wake-up times from this moment.
- Adjust the minutes it usually takes you to fall asleep. Most people need 10 to 20.
- If you know your own rhythm, change the cycle length. Cycles vary from about 80 to 110 minutes between people.
What are sleep cycles?
Through the night you move through repeating cycles of light sleep, deep sleep and REM (dreaming) sleep. Early cycles have more deep sleep; later ones have more REM. Waking during deep sleep is what causes that heavy, groggy feeling called sleep inertia. Timing your alarm for the end of a cycle, when sleep is lightest, can make mornings easier. The 90-minute figure is an average, so treat the times as a guide rather than an exact science.
How much sleep do you need?
| Age | Recommended sleep per day |
|---|---|
| Babies 4 to 12 months | 12 to 16 hours, including naps |
| Toddlers 1 to 2 years | 11 to 14 hours, including naps |
| Children 3 to 5 years | 10 to 13 hours, including naps |
| Children 6 to 12 years | 9 to 12 hours |
| Teens 13 to 18 years | 8 to 10 hours |
| Adults 18 and over | 7 hours or more (7 to 9 is typical) |
Source: American Academy of Sleep Medicine guidelines. Quality matters as much as hours.
Tips for better sleep
- Keep the same bedtime and wake time every day, including weekends.
- Avoid caffeine in the 6 to 8 hours before bed and heavy meals late at night.
- Keep your bedroom cool, dark and quiet, and put screens away 30 to 60 minutes before sleep.
- Get daylight in the morning to set your body clock.
If you often feel tired despite enough hours, snore loudly or wake gasping, talk to a doctor; these can be signs of a sleep disorder. Try a timed nap with the countdown timer, and plan focused work blocks with the Pomodoro timer.
FAQ
Is it better to sleep 6 or 7.5 hours?
Most adults need at least 7 hours. If you only have time for 6, waking at the end of a cycle may feel easier than 6.5 hours, but more sleep is still better over time.
How long is a power nap?
About 10 to 20 minutes, which keeps you in light sleep. A full 90-minute nap completes one cycle.
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