Sleep Calculator

Find the best time to go to bed or wake up, based on sleep cycles. Free, no sign-up, works in your browser.

I want to wake up at

I’m going to bed at

Time to fall asleep minCycle length min

Adults usually need 7–9 hours (5–6 cycles). Waking at the end of a cycle helps you feel less groggy. This is general information, not medical advice.

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How to use the sleep calculator

Choose whether you know your wake-up time or your bedtime.
Adjust how long you usually take to fall asleep.
Pick one of the suggested times — 5 or 6 full cycles are best for most adults.

Sleep runs in cycles of roughly 90 minutes (light sleep, deep sleep and REM). Waking up in the middle of deep sleep makes you feel heavy, while waking between cycles feels more natural. Individual cycles vary from about 80 to 110 minutes, so adjust the cycle length if the suggestions don’t match how you feel.