Calculate optimal sleep and wake times. Enter your desired wake time or bedtime to get suggested schedules built around 90-minute sleep cycles.
Choose whether you want to wake at a set time or fall asleep now, then enter the time. The calculator counts back (or forward) in 90-minute sleep cycles and allows 15 minutes to fall asleep, recommending the bedtimes or wake times that let you complete whole cycles.
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A sleep calculator uses the natural 90-minute sleep cycle to suggest bedtimes or wake times so you rise at the end of a cycle — the easiest point to wake feeling refreshed rather than groggy.
Waking at the end of a cycle avoids interrupting deep sleep, which is what causes morning grogginess.
Sleep cycles — moving through light, deep and REM sleep — average about 90 minutes, though it varies by person and age. Timing wake-up to the end of a cycle makes waking easier.
Consistency helps most. Aim for one of the suggested times, but keeping a regular schedule and getting enough total sleep matters more than landing on the precise minute.