Sleep Cycle Calculator
Estimate when to go to bed or when to wake up using full sleep cycles. Adjust the cycle length and time to fall asleep for a more realistic personal planning estimate.
Try a common sleep plan
6 cycles · 9 hr
21:45
5 cycles · 7 hr 30 min
23:15
4 cycles · 6 hr
00:45
3 cycles · 4 hr 30 min
02:15
A sleep cycle calculator estimates bedtimes or wake-up times using full sleep cycles.
The common planning model uses 90-minute cycles plus time to fall asleep.
Sleep timing is calculated in the browser for this tool based on the current public implementation.
Use your real buffer
If it usually takes 20 minutes to fall asleep, include that instead of assuming instant sleep.
Treat cycles as estimates
Sleep stages vary by person and night, so use this for scheduling rather than diagnosis.
Bedtime = wake time - cycle count x cycle length - time to fall asleep
If you want to wake at 7:00 and plan for 5 cycles, the default model subtracts 7.5 hours plus 15 minutes for falling asleep. That suggests trying to be in bed around 23:15.
This calculator is useful for planning alarms, travel schedules, study routines, and early workdays. It does not measure actual sleep quality, sleep stages, or medical sleep conditions.
If sleep problems are persistent, use this only as a scheduling aid and speak with a qualified clinician.
Example
For a 6:30 wake-up, 5 cycles of 90 minutes plus 15 minutes to fall asleep suggests getting into bed around 22:45.
Assumption
The default cycle length is 90 minutes, but the tool lets you adjust it because real sleep cycles vary.
Limitation
The calculator does not track sleep stages, sleep quality, insomnia, breathing issues, or medical sleep conditions.
Early workdays
Pick a bedtime for an early alarm with 4 to 6 cycle options.
Travel planning
Plan sleep windows around flights, trips, and local wake-up times.
Study routines
Estimate when to stop work and get into bed before exams or school days.
Alarm planning
Compare wake-up times after a planned bedtime.
Treating 90 minutes as exact
Ninety minutes is a planning estimate. Real cycles vary by person, stress, sleep debt, and the night itself.
Ignoring time to fall asleep
If it usually takes 10 to 20 minutes to drift off, include that buffer instead of counting from the moment you get into bed.
Using the result as medical advice
This page helps with scheduling alarms and routines. It does not measure sleep quality or diagnose sleep problems.
What time should I sleep to wake up at 6:30?
With the default 90-minute cycle and 15 minutes to fall asleep, common options are 21:15 for 6 cycles, 22:45 for 5 cycles, and 00:15 for 4 cycles.
Is 5 sleep cycles enough?
Five 90-minute cycles equals 7.5 hours of sleep before adding time to fall asleep. Some people plan around this amount, while others need more or less.
Can I change the cycle length?
Yes. The calculator lets you adjust cycle length from 70 to 120 minutes because real sleep cycles vary.
Why include time to fall asleep?
If it usually takes 10 to 20 minutes to fall asleep, adding that buffer makes the bedtime estimate more practical.
Suggested workflow
Sleep planning path
Estimate bedtimes or wake-up times, then connect the plan to daily energy and time blocks.