Sleep Cycle Calculator
To wake up refreshed, try going to bed at one of these times:
Sleep cycles average about 90 minutes but vary by person. These times are a guide, not medical advice.
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Find the best times to fall asleep or wake up based on 90-minute sleep cycles. Waking at the end of a cycle, rather than in the middle, helps you feel more refreshed. Choose a wake-up time, a bedtime, or sleep right now, and get suggested times. It runs entirely in your browser.
How to use
- Pick a mode: wake at a set time, go to bed at a set time, or sleep now.
- Enter the time (the current time is used for sleep now).
- Choose one of the suggested times — five or six cycles is recommended.
How it works
Sleep moves through cycles of roughly 90 minutes, each cycling through light, deep and REM sleep. Waking at the end of a cycle feels easier than waking mid-cycle. The calculator counts back or forward in 90-minute blocks and adds about 15 minutes to fall asleep, so the suggested times land between cycles.
Features
Three modes
Work backward from a wake time, forward from a bedtime, or from right now.
Recommended cycles
Five to six cycles (about 7.5 to 9 hours) are highlighted as ideal for most adults.
12 or 24-hour
Switch between 24-hour and 12-hour (AM/PM) display.
Fall-asleep time
Adds about 15 minutes to drift off, so the times are realistic.
When to use it
Early start
Plan your bedtime the night before an early wake-up.
Late night
When it is already late, find the best time to wake after sleeping now.
Naps & planning
Plan sleep around a fixed schedule to avoid groggy mid-cycle wake-ups.
Kids' bedtime
Work out a bedtime that fits a needed wake-up time.
Notes
- Cycle length is an average of about 90 minutes and varies between people.
- The estimate assumes around 15 minutes to fall asleep.
- Use it as a helpful guide, not a strict rule or medical advice.
- Everything runs on your device; nothing is uploaded.
FAQ
- What is a 90-minute sleep cycle?
- It is the approximate time your body takes to move through the stages of sleep once. Waking at the end of a cycle tends to feel easier than waking in the middle.
- How many cycles do I need?
- Most adults do well with five to six cycles a night, roughly 7.5 to 9 hours. Those options are highlighted as recommended.
- How does the 'sleep now' mode work?
- It uses your current time as the bedtime and suggests wake-up times that fall at the end of cycles.
- Is it accurate for everyone?
- Cycle length varies by person, so treat the times as a guide. Adjust based on how you actually feel.
- Is my data sent to a server?
- No. The calculation happens entirely in your browser.