Plan your sleep
Choose whether you have a wake-up time or a bedtime in mind.
How the sleep cycle calculation works
Sleep happens in repeating cycles of about 90 minutes, each moving from light sleep into deep sleep and then REM. Waking near the end of a cycle, during light sleep, usually feels easier than waking from deep sleep. This calculator works backwards or forwards in 90-minute steps, plus the time it takes you to fall asleep, to suggest times that land at the end of a full cycle. Five cycles is about 7.5 hours and six cycles is about 9 hours.
Frequently asked questions
How long is one sleep cycle?
One sleep cycle lasts about 90 minutes on average, moving through light sleep, deep sleep, and REM. Individual cycles can range from roughly 80 to 100 minutes, but 90 minutes is the widely used average.
Why does waking at the end of a cycle feel better?
Waking during light sleep, which tends to fall near the end of a cycle, usually feels easier than being woken from deep sleep. Lining your alarm up with the end of a cycle is the idea behind this calculator, though real cycle lengths vary night to night.
Why does the calculator add fall-asleep time?
Most people take around 14 minutes to fall asleep after getting into bed. The calculator counts cycles from when you are likely asleep, not from when you lie down. Adjust the value if you fall asleep faster or slower.
How many sleep cycles do I need?
Many adults aim for 5 to 6 complete cycles, about 7.5 to 9 hours. Five is often a practical minimum and six a fuller night, but sleep needs differ from person to person.
Is this medical advice?
No. This tool is for general information and uses simple average cycle lengths. It does not diagnose or treat any condition. If you have ongoing sleep problems, speak with a qualified healthcare professional.
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Disclaimer: This sleep cycle calculator is for general informational purposes only and is not medical advice. It uses average 90-minute cycle lengths, which vary between people and nights. Consult a qualified healthcare professional about any ongoing sleep concerns.