Sleep Calculator — Bedtime & Wake-Up Time
Find the best time to sleep or wake based on 90-minute sleep cycles. Enter a time and get bedtime or wake-up suggestions. Free, in your browser.
Wake up at one of these times:
- 8:14 AM6 cycles · 9 h sleep
- 6:44 AM5 cycles · 7.5 h sleep
- 5:14 AM4 cycles · 6 h sleep
- 3:44 AM3 cycles · 4.5 h sleep
🔒 Calculated in your browser. Suggestions based on ~90-minute sleep cycles and ~14 min to fall asleep — a rough guide, not medical advice. Individual sleep varies.
Wake up between sleep cycles
Sleep runs in roughly 90-minute cycles. Waking at the end of a cycle — rather than in the middle of deep sleep — tends to feel easier. Enter the time you plan to fall asleep to see good wake-up times, or a target wake-up time to see when to head to bed. It also allows about 14 minutes to actually fall asleep.
Suggestions, not a rule
The 90-minute cycle and 14-minute latency are common averages — real sleep varies from person to person and night to night. Use the times as a guide, and aim for 5–6 full cycles (about 7.5–9 hours). Everything is calculated in your browser.
Frequently asked questions
How does a sleep cycle calculator work?
It counts back or forward in ~90-minute cycles from your chosen time, plus ~14 minutes to fall asleep, so you wake near the end of a cycle rather than mid-deep-sleep.
How many sleep cycles do I need?
Most adults do well on 5–6 cycles, roughly 7.5–9 hours. The tool lists several options so you can pick what fits your schedule.