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Sleep time calculator

Choose when you want to sleep or wake to view several cycle-based options. Individual sleep patterns vary, so treat them as estimates.

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Understand the sleep-time estimates

Choose a wake-up time to calculate possible bedtimes, or a bedtime to calculate wake-up times. The tool uses fixed assumptions of 90 minutes per cycle and 15 minutes to fall asleep; it does not measure your sleep.

How to use it

  1. Choose whether the time you enter is your desired wake-up time or your bedtime.
  2. Set that time and compare the options for three, four, five and six cycles.
  3. To check a bedtime result, subtract the cycle duration and 15 minutes from the wake-up time. Reverse the calculation for a wake-up result.

Example

Starting point
Desired wake-up time: 07:00, using six cycles.
What to expect
Six times 90 minutes is 9 hours. Subtracting 9 hours and 15 minutes gives 21:45 on the previous day. Five cycles give 23:15.

Before you start

  • The 90-minute cycle and 15-minute delay are fixed calculation assumptions, not personal measurements. The options do not guarantee waking in a particular sleep stage or feeling rested.
  • Three cycles represent 4 hours 30 minutes of calculated sleep, not a recommended sleep duration. Results contain no date and do not adjust for clock changes; this tool does not set an alarm or provide medical advice.