Sleep Cycle Bedtime Calculator
Find the best bedtimes to wake up feeling refreshed by aligning with 90-minute sleep cycles.
How to use this tool
- Enter wake-up time and sleep cycles in the fields above.
- Results update instantly as you type — or click Calculate.
- Read your bedtime and the full breakdown beneath it.
Sleep happens in 90-minute cycles. Waking at the end of a cycle — rather than mid-cycle — leaves you feeling more refreshed. This calculator works backwards from your desired wake time (plus 15 minutes to fall asleep).
Frequently asked questions
- How long is a sleep cycle?
- Each sleep cycle lasts approximately 90 minutes, moving through light sleep, deep sleep, and REM. Most adults complete 4–6 cycles per night.
- How many hours of sleep do I need?
- Adults generally need 7–9 hours (roughly 5–6 cycles). Teenagers need 8–10 hours; children need more.