Sleep Cycle Calculator
Find the best bedtime for a given wake-up time, or the best wake-up times for a given bedtime, based on the average 90-minute sleep cycle.
About this sleep cycle calculator
Sleep happens in cycles of roughly 90 minutes, and waking up in the middle of a cycle (rather than between cycles) is widely associated with feeling groggier. This calculator works backward or forward from your target time in 90-minute increments.
How sleep cycle calculator works
The calculator adds or subtracts multiples of 90 minutes (plus an estimated 15 minutes to fall asleep) from your given time, showing several options so you can pick a number of cycles that fits your schedule.
Common uses
- Finding the best bedtime for a fixed wake-up alarm
- Finding good wake-up times based on when you plan to go to bed
- Planning sleep around an early flight or appointment
How to use this tool
- Choose whether you know your wake-up time or your bedtime.
- Enter that time.
- See several suggested bedtimes or wake times, based on full 90-minute sleep cycles.
What to know before using it
90 minutes is an average cycle length, individual sleep cycles vary somewhat from person to person and night to night. This is a general wellness planning tool, not a substitute for addressing an actual sleep disorder with a healthcare professional.
Privacy and browser-first processing
This tool runs entirely in your browser using JavaScript. Nothing you enter is uploaded or stored.
Frequently asked questions
Why 90 minutes specifically?
A full sleep cycle, moving through light sleep, deep sleep, and REM, averages around 90 minutes, waking up near the end of a cycle rather than in the middle of one is commonly associated with feeling more refreshed.
Is this exact for everyone?
No, 90 minutes is a population average, your own cycles may run somewhat shorter or longer, use this as a helpful starting point rather than an exact science.