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Sleep Calculator

Need to be up at 7? Choose whether you are going to bed now or need to wake at a set time, and get times that line up with the end of a 90-minute sleep cycle, allowing about 15 minutes to fall asleep.

Runs in your browser — nothing you enter is uploaded

A sleep cycle lasts about 90 minutes and most people take about 15 minutes to fall asleep. Waking at the end of a cycle usually feels easier; adults need five or six cycles.

Try waking up at

  • 8:15 AM

    6 cycles (9 hours of sleep)

  • 6:45 AM

    5 cycles (7.5 hours of sleep)

  • 5:15 AM

    4 cycles (6 hours of sleep)

How to use

  1. Choose "Going to bed now" or "I need to wake at".
  2. Enter the bedtime or wake-up time.
  3. Pick one of the suggested times; five or six cycles suit most adults.

Options explained

Sleep cycle
Light sleep, deep sleep and REM make up a cycle of about 90 minutes. Waking at the end of one feels easier than waking from deep sleep.
Time to fall asleep
About 15 minutes is assumed. If you take longer, go to bed a little earlier.

Examples

Situation Suggested times
Bed at 11 pm Wake at 8:15, 6:45 or 5:15 am
Wake at 7 am Go to bed at 9:45 pm, 11:15 pm or 12:45 am

Frequently asked questions

Is everyone's cycle 90 minutes?

No — it ranges from about 80 to 110 minutes and changes through the night. Treat the times as a starting point and adjust by 10–20 minutes.

How much sleep do adults need?

Most adults need 7–9 hours, or five to six cycles.

How long should a nap be?

About 20 minutes avoids deep sleep; a full 90-minute cycle also works if you have time.

Privacy

This tool runs entirely in your browser. Your files and text are processed on your device and are never uploaded to our servers.

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