About this sleep cycle calculator
Work out bedtimes or wake-up times based on 90-minute sleep cycles, the approximate length of a full cycle of light, deep, and REM sleep. Choose whether you're planning around a wake-up time or a bedtime, enter that time, and this tool works out four options — 3, 4, 5, or 6 complete cycles — each including roughly 14 minutes to fall asleep. Waking up at the end of a cycle, rather than in the middle of one, is commonly associated with feeling less groggy. Use this workspace to prepare a result you can review before putting it to use. All processing takes place on your device, without an account or an upload of your inputs. Check the examples to understand the expected output, read the limitations for the supported scope, and reset the form when you want to start a separate task.
How the sleep cycle calculator works
Adds or subtracts 14 minutes (to fall asleep) plus a whole number of 90-minute cycles (3 to 6) from the time you enter, wrapping across midnight as needed.
Sleep Cycle Calculator examples
Wake-up time 07:00
For 6 cycles (9.0h sleep), go to bed at 21:46
Bedtime 23:00
For 6 cycles (9.0h sleep), wake at 08:14
Limitations & privacy
Assumes a fixed 14-minute time to fall asleep and exact 90-minute cycles; actual cycle length and time to fall asleep vary by person and by night. This is a planning estimate, not a sleep-tracking or medical tool.
Inputs and results stay in this browser. Only tool identifiers are stored for your recently used tools. You can clear that history from the directory.
Sleep Cycle Calculator: frequently asked questions
How does the sleep cycle calculator work?
Adds or subtracts 14 minutes (to fall asleep) plus a whole number of 90-minute cycles (3 to 6) from the time you enter, wrapping across midnight as needed.
What can I inspect in the sleep cycle calculator result?
The sleep window comparison helps you check the result before using it. Assumes a fixed 14-minute time to fall asleep and exact 90-minute cycles; actual cycle length and time to fall asleep vary by person and by night. This is a planning estimate, not a sleep-tracking or medical tool.
Does the sleep cycle calculator upload my input?
Processing happens in your browser. No tool input or output is uploaded to a server. Use Reset to clear the current workspace before starting a separate task.
Updated September 20, 2026