The sleep calculator tells you what time to go to bed so you wake up at the end of a sleep cycle instead of in the middle of one. Enter the time you need to get up and it lists the best bedtimes, or enter when you are going to bed and it shows the best times to set your alarm.
How the sleep calculator works
During the night you move through repeating sleep cycles of light sleep, deep sleep and REM (dreaming) sleep. Each cycle lasts roughly 80 to 120 minutes, and about 90 minutes on average. Waking up when a cycle ends, while you are in light sleep, usually feels easier than being woken out of deep sleep, which can leave you groggy.
Most adults take about 10 to 20 minutes to fall asleep, so the calculator adds 15 minutes by default. Change it if you usually drop off faster or more slowly.
Bedtimes for common wake-up times
Five cycles (7½ hours) or six cycles (9 hours) of sleep, plus 15 minutes to fall asleep:
| Wake up at | Bed for 6 cycles (9 h) | Bed for 5 cycles (7½ h) |
|---|---|---|
| 5:00 a.m. | 7:45 p.m. | 9:15 p.m. |
| 6:00 a.m. | 8:45 p.m. | 10:15 p.m. |
| 6:30 a.m. | 9:15 p.m. | 10:45 p.m. |
| 7:00 a.m. | 9:45 p.m. | 11:15 p.m. |
| 7:30 a.m. | 10:15 p.m. | 11:45 p.m. |
| 8:00 a.m. | 10:45 p.m. | 12:15 a.m. |
How much sleep do you need?
The CDC recommends at least 7 hours a night for adults aged 18 to 60, 7 to 9 hours from 61 to 64, and 7 to 8 hours from age 65. Teenagers need 8 to 10 hours and children aged 6 to 12 need 9 to 12. For most adults, that means five or six full cycles. Our guide how much sleep do you need has the full table by age and tips for sleeping better.
Tips for waking up refreshed
- Keep the same wake-up time every day, including weekends. A steady schedule matters more than hitting an exact cycle.
- Get daylight soon after you wake up, and dim screens and lights in the hour before bed.
- Avoid caffeine in the afternoon and large meals or alcohol close to bedtime.
- If you are often tired despite enough hours in bed, talk to a doctor; conditions such as sleep apnea are common and treatable.
Frequently asked questions
Is it better to sleep 6 or 7.5 hours?
For most adults, 7½ hours is better because it gives you more total sleep. Four cycles (6 hours) is less than the 7 hours adults are advised to get, even if you wake up between cycles.
Are sleep cycles always 90 minutes?
No. Ninety minutes is an average; cycles vary between people and through the night. If you often wake up a little before your alarm, try a cycle length of 85 or 95 minutes.
What time should I go to bed to wake up at 6 a.m.?
For 7½ hours of sleep, go to bed around 10:15 p.m.; for 9 hours, around 8:45 p.m. Both include 15 minutes to fall asleep.
This calculator is for general information and isn’t medical advice.