Sleep Calculator
Wake up refreshed (90m cycles).
The Science of Sleep Cycles
Sleep isn't a uniform state. Your brain cycles through distinct stages approximately every 90 minutes. Waking up in the middle of a deep sleep stage can leave you feeling groggy and disoriented (sleep inertia).
The Stages of Sleep
- Light Sleep (Stages 1 & 2): Transition from wakefulness. Body temperature drops, heart rate slows.
- Deep Sleep (Stage 3): Critical for physical restoration, muscle repair, and immune function. Hardest to wake up from.
- REM Sleep: Dreaming occurs here. Brain activity increases. Essential for memory consolidation and emotional regulation.
How Many Cycles Do You Need?
Most adults need 5-6 full cycles (7.5 to 9 hours) per night. This calculator helps you time your alarm to wake up at the end of a cycle, when you are in the lightest sleep stage.
Tips for Better Sleep
Maintain a consistent schedule, avoid blue light (screens) before bed, keep your room cool and dark, and limit caffeine intake after noon.