Wake up between sleep cycles, not during one.
Sleep runs in loops of about 90 minutes. Pick a time and we'll find the bedtimes or alarms that land at the end of a cycle.
Cycle length varies from person to person (roughly 80-110 min). If you routinely wake just before your alarm, your cycle is probably a little shorter than 90.
Go to bed at one of these times
How it works
We add the time it takes you to drift off, then step forward (or back) in whole sleep cycles. Each cycle moves from light sleep into deep slow-wave sleep and back up into REM. The end of REM is the shallowest point of the night, and the easiest moment to wake.
Five or six cycles (7.5 to 9 hours) is the target for most adults. Four is a rough night you can get through. Three should be the exception. The 90-minute figure is an average, not a law. Read why.
Common questions
How many sleep cycles do I need?
Most adults need five or six cycles a night, about 7.5 to 9 hours of sleep. Sleep medicine groups recommend at least 7 hours for adults. Four cycles (6 hours) gets you through a day but leaves you short if it becomes a habit.
How long is one sleep cycle?
About 90 minutes on average, but it varies from roughly 70 to 120 minutes between people and across the night. If you often wake a little before your alarm feeling fine, your cycles may be shorter than 90 minutes. You can change the cycle length in the calculator.
Why do I feel groggy even after a full night?
Waking from deep sleep causes sleep inertia: grogginess that can last 15 to 30 minutes or more. Deep sleep is concentrated early in the night, so a well-timed alarm at the end of a later cycle usually feels easier.
How long should it take to fall asleep?
Healthy adults usually fall asleep in 10 to 20 minutes. Regularly taking more than 30 minutes can be a sign of insomnia, while falling asleep within a few minutes every night often means you are short on sleep.
