Sleep Calculator
Optimize your rest by calculating bedtimes and wake-up times that align with natural 90-minute sleep cycles.
Suggested
Quality
Understanding Sleep Cycles
A single sleep cycle lasts about 90 minutes. Waking up mid-cycle often leads to grogginess, while waking at the end of a cycle makes you feel refreshed.
9 Hours
6 Cycles (Ideal)
7.5 Hours
5 Cycles (Great)
Why Sleep Cycles Matter
It’s not just about how long you sleep, but when you wake up. During the night, your brain moves through different stages of sleep: light sleep, deep sleep, and REM (Rapid Eye Movement).
The 90-Minute Rule
Each full cycle takes approximately 90 minutes. If you wake up at the end of a cycle, you’re in light sleep, which is the natural time for your body to transition to being awake.
Sleep Inertia
Waking up in the middle of deep sleep causes "sleep inertia"—that heavy, confused feeling that can last for hours after you get out of bed.