Sleep Calculator: What Time Should I Go to Bed?
Calculate the best bedtime based on sleep cycles. Wake up feeling rested instead of groggy.
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You wake up at 7 AM feeling like garbage even though you got 8 hours of sleep. The problem isn't how MUCH you slept. It's WHEN your alarm went off relative to your sleep cycles.
How Sleep Cycles Work
You cycle through 4 stages of sleep roughly every 90 minutes. Light sleep, deep sleep, REM sleep, repeat. Waking up during deep sleep is what makes you feel terrible. Waking up during light sleep (between cycles) makes you feel refreshed.
Calculate Your Bedtime
The Sleep Calculator works backwards from your wake-up time. If you need to wake at 7 AM:
- 5 cycles (7.5 hours): Go to bed at 11:30 PM
- 6 cycles (9 hours): Go to bed at 10:00 PM
Add 15 minutes for falling asleep. So realistically, be in bed by 11:15 PM or 9:45 PM.
The Magic Number Isn't 8 Hours
8 hours is 5.33 sleep cycles. That means your alarm goes off in the middle of cycle 6. You'll probably feel groggy. 7.5 hours (5 complete cycles) or 9 hours (6 complete cycles) are better targets than 8.
Some people thrive on 5 cycles. Some need 6. Experiment for a week with each and see which one has you feeling better.