Sleep calculator
Find the bedtime for a wake-up time, or the wake-up times for when you fall asleep, in 90-minute sleep cycles.
How the sleep calculator works
A night of sleep is a series of cycles, each lasting roughly 90 minutes and moving from light sleep into deep sleep and back through REM. Waking at the end of a cycle, when sleep is light, feels far better than an alarm landing in the middle of deep sleep, which is the heavy, disoriented feeling most people blame on "not enough sleep". The calculator adds the 14 minutes an average adult takes to fall asleep and then counts whole cycles, so every time it suggests is a cycle boundary.
Five cycles is seven and a half hours of actual sleep and six cycles is nine; that range covers most adults. Three or four cycles is a short night that you can get away with occasionally. Cycle length varies from person to person by ten or fifteen minutes, so treat the times as a starting point and shift them if you consistently wake groggy.
Set the alarm from here
Every wake-up time has its own page with the same bedtime table, a countdown, and a one-tap alarm: for example 6:00 AM, 6:30 AM, 7:00 AM or 7:30 AM.