The Science of 90-Minute Cycles
One sleep cycle lasts about 90 minutes. During this time, your body goes through several stages: light sleep, deep sleep, and REM (Rapid Eye Movement).
Why Timing Matters
If you wake up in the middle of a cycle (especially deep sleep), you will likely experience "sleep inertia" â that feeling of being incredibly groggy and "foggy." Waking up *between* cycles makes you feel naturally alert and refreshed.
How many cycles do you need?
- 5 Cycles: 7.5 hours (Standard)
- 6 Cycles: 9 hours (Ideal for some)
- 4 Cycles: 6 hours (Minimum to avoid exhaustion)