Sleep Cycle Calculator

Wake up feeling refreshed by timing your sleep with your brain's natural rhythms.

You should try to fall asleep at:

Calculations include 14 minutes to fall asleep.

How the 90-Minute Rule Works

A good night's sleep isn't just about total hours; it's about finishing your sleep cycles. When you sleep, your brain goes through several stages, ending with **REM (Rapid Eye Movement)** sleep.

[Image of a sleep cycle graph showing REM and deep sleep stages]
  • The Cycle: One complete cycle takes about **90 minutes**. If you wake up during the middle of a cycle (specifically during deep sleep), you feel exhausted and groggy, even if you slept for a long time.
  • The Sweet Spot: Most adults need **5 or 6 cycles** (7.5 or 9 hours) to feel fully rested. Waking up after only 4 cycles (6 hours) is better for your brain than waking up after 6 hours and 40 minutes!
  • Falling Asleep: On average, it takes a healthy person **14 minutes** to fall asleep. This calculator automatically adds that "buffer time" to your suggestions.