Sleep Calculator
Find the optimal time to go to bed based on when you need to wake up. We calculate backwards in 90-minute sleep cycles and add 14 minutes for you to fall asleep.
Enter your wake-up time and click calculate to see your optimal bedtimes.
How this calculator works
Human sleep isn't uniform. We sleep in cycles that last roughly 90 minutes. During these cycles, we move through light sleep, deep sleep, and REM (Rapid Eye Movement) sleep.
If you wake up in the middle of a deep sleep stage, you're likely to feel groggy, disoriented, and sluggish—a phenomenon known as "sleep inertia." This is why you sometimes feel worse after 8 hours of sleep than you do after 6.
Our sleep calculator works backwards from your desired wake-up time in 90-minute blocks, ensuring you wake up at the end of a cycle, when your brain is naturally closest to wakefulness.
Frequently Asked Questions
Why is 14 minutes added to the calculation?
Studies show the average adult takes between 10 to 20 minutes to fall asleep (called sleep latency). We use 14 minutes as a conservative average so you can simply get into bed at the recommended time.
What if my sleep cycles aren't exactly 90 minutes?
While 90 minutes is the average, individual cycles can range from 90 to 110 minutes, and they often get longer as the night progresses. This calculator provides a solid baseline to experiment with. Adjust by 15-minute increments if you find it's consistently off for your body.