Go to bed at 8:00 PM for 7.5 hours of sleep, or 6:30 PM for 9 hours.
Both times give you whole 90-minute sleep cycles, so you wake up in lighter sleep, and include 15 minutes to fall asleep.
To wake up at 3:45 AM, go to bed at one of these times:
Includes 15 minutes to fall asleep. Adults need 7 to 9 hours, so 7.5 hours (5 cycles) is marked as the best fit.
| Go to bed at | Sleep | Cycles | |
|---|---|---|---|
| 6:30 PM | 9 hours | 6 | Good for teens and people who need more sleep |
| 8:00 PM | 7.5 hours | 5 | Recommended for most adults |
| 9:30 PM | 6 hours | 4 | Short: below the 7-hour minimum |
| 11:00 PM | 4.5 hours | 3 | Very short: only for an emergency |
| Who | Needs | Latest bedtime | Bedtime in sync with cycles |
|---|---|---|---|
| School-age child (6–12) | 9+ hours | 6:30 PM | 6:30 PM |
| Teenager (13–18) | 8+ hours | 7:30 PM | 6:30 PM |
| Adult (18–64) | 7+ hours | 8:30 PM | 8:00 PM |
| 65 and older | 7+ hours | 8:30 PM | 8:00 PM |
Recommended sleep: AASM and CDC. Latest bedtime gives the minimum sleep for that age, plus 15 minutes to fall asleep.
| Time to fall asleep | Bedtime for 5 cycles | Bedtime for 6 cycles |
|---|---|---|
| 5 minutes | 8:10 PM | 6:40 PM |
| 15 minutes | 8:00 PM | 6:30 PM |
| 30 minutes | 7:45 PM | 6:15 PM |
Waking up before 5 AM means an early bedtime. If you start work this early, keep the same bedtime on days off where you can, so your body clock stays steady. On a very early start, a short afternoon nap can help: see the nap calculator.
For general information only, not medical advice. If you often feel tired despite enough sleep, snore loudly, or have trouble sleeping most nights, talk to a doctor.