Sleep Cycle Calculator — what it does, the basis for its calculations, and why we made it.
The Sleep Cycle Calculator is a free web tool that works out bedtimes and wake-up times that help you wake up refreshed. Enter the time you want to wake up and it tells you when to go to bed — or enter your bedtime and it tells you when to set your alarm.
The calculation is based on the principle that sleep repeats in cycles of about 90 minutes. Waking at the end of a cycle tends to feel easier, and the average time it takes to fall asleep (about 14 minutes) is also factored in.
How long you sleep matters, but so does when you wake up. This site exists so the choice you make every night can rest on a simple rule instead of guesswork.
The 90-minute cycle and the time to fall asleep are averages and vary from person to person. This tool is for reference only and does not replace medical diagnosis or treatment. If sleep problems persist, consult a specialist.