Sleep Calculator
Wake up feeling refreshed by timing your sleep to complete full 90-minute cycles.
These bedtimes let you wake naturally between sleep cycles.
09:46 PM
⭐6 cycles
9h
11:16 PM
⭐5 cycles
7h 30m
12:46 AM
4 cycles
6h
02:16 AM
3 cycles
4h 30m
03:46 AM
2 cycles
3h
05:16 AM
1 cycle
1h 30m
How it works
🔄Each sleep cycle lasts ~90 minutes
😴Average person takes ~14 minutes to fall asleep
⭐5–6 cycles (7.5–9 hours) is ideal for most adults
💡Waking mid-cycle causes grogginess — time it right!
Why Sleep Cycles Matter
Human sleep consists of repeating 90-minute cycles, each containing stages of light sleep, deep sleep, and REM sleep. Waking up at the end of a complete cycle — rather than mid-cycle during deep sleep — dramatically reduces sleep inertia, the grogginess that makes mornings difficult.
This calculator adds 14 minutes to account for average time to fall asleep, then calculates wake times that align with the end of complete 90-minute cycles. Five to six complete cycles (7.5 to 9 hours) are recommended for most adults.