Sleep Calculator
Calculate the best times to sleep or wake up based on 90-minute sleep cycles.
If you want to wake up at a specific time...
Sleep cycle
Each sleep cycle lasts approximately 90 minutes. Waking between cycles makes you feel more rested.
Go to bed at
21:45
6 cycles
9h 0m
Excellent
23:15
5 cycles
7h 30m
Good
00:45
4 cycles
6h 0m
Adequate
Sleep stages
Each 90-min cycle includes light, deep, and REM sleep. Deep sleep predominates in early cycles, REM in later ones.
Tips for better sleep
Maintain a regular sleep schedule, even on weekends.
Avoid screens at least 30 minutes before bed.
Keep the room cool (65-68°F) and dark.
What are sleep cycles?
Sleep is divided into approximately 90-minute cycles. Each cycle includes light, deep, and REM sleep. Completing full cycles makes you feel more rested.
Cycle phases
Phase 1-2: Light sleep, easy to wake. Phase 3: Deep sleep, physical repair. REM: Vivid dreams, memory consolidation.
Importance of sleep
Sleep is essential for physical and mental health. Adults need 7-9 hours. Sleep deprivation affects memory, mood, immune system, and performance.