Find the best times to sleep or wake based on 90-minute sleep cycles.
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How do you calculate the best time to sleep or wake up?
Each sleep cycle is about 90 minutes, and people take roughly 14 minutes to fall asleep, so the tool counts back or forward in whole cycles from your chosen time. Most adults do best on 5–6 cycles (7.5–9 hours). To wake at 7:00 AM, good bedtimes are about 9:46 PM (6 cycles) or 11:16 PM (5 cycles).
Understanding your result
Most adults do best on 5–6 cycles (7.5–9 hours). Waking between cycles avoids the grogginess of waking mid-cycle.
Formula and method
Each cycle is about 90 minutes, and people take roughly 14 minutes to fall asleep. The tool counts back or forward in whole cycles from your chosen time.
Worked example
To wake at 7:00 AM, good bedtimes are about 9:46 PM (6 cycles) or 11:16 PM (5 cycles).
How to use this tool
- Choose whether you’re setting a wake time or a sleep time.
- Enter the time.
- Press Calculate to see the recommended times.
About the Sleep Calculator
The Sleep Calculator suggests bedtimes or wake-up times that fall between 90-minute sleep cycles, so you wake at the lightest part of sleep and feel more rested.
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Frequently asked questions
Why 90 minutes?
A full sleep cycle through light, deep and REM sleep averages about 90 minutes, though it varies between people.