Understand the result
How to use the sleep calculator
Estimate one bedtime or wake-up time from a selected number of 90-minute sleep cycles.
Formula or method
Selected cycles are multiplied by 90 minutes. Bedtime calculations also subtract an estimated 15 minutes for falling asleep.
Worked examples
Wake at 7:00 AM
Five 90-minute cycles plus a 15-minute settling estimate suggests going to bed around 11:15 PM.
Plan six cycles
Six cycles represent about nine hours of sleep, before adding time to fall asleep.
Calculate a wake time
Choose a bedtime and four cycles to estimate a wake time about six hours later.
Frequently asked questions
Why does the calculator use 90-minute cycles?
Ninety minutes is a common planning estimate, but real sleep cycles vary between people and across the night.
Is 15 minutes always enough to fall asleep?
No. It is only a default settling estimate and may be too short or long for you.
Does the result guarantee I will wake refreshed?
No. Sleep quality depends on health, schedule, environment and many other factors.
Is this medical advice?
No. Persistent sleep problems should be discussed with a qualified healthcare professional.
Limitations
Sleep cycles and individual sleep needs vary; this is not medical guidance.