Find the best time to go to sleep using 90 minute sleep cycles. Enter when you need to wake up and see your bedtimes in seconds. Works for Tehran, Mashhad, Isfahan and anywhere else.
Enter the time you need to wake up and see the best times to fall asleep.
Suggested bedtimes. Pick the one that suits you:
These times are estimates and not medical advice.
In 1953 Nathaniel Kleitman and Eugene Aserinsky at the University of Chicago showed that sleep runs in repeating cycles of about 90 minutes. Each cycle has four stages:
The shift from awake to asleep. It lasts five to ten minutes and is easy to wake from.
Heart rate and body temperature drop. It makes up a large part of every cycle.
The repair stage. Waking here leaves you heavy and foggy.
Dreams and memory storage. It grows longer in the later cycles of the night.
Key point: waking at the end of a full cycle usually feels fresher than waking in the middle of one, even after eight hours in bed. BedtimeCalc counts back from your wake time on that basis.
14 to 17 hours a day, including naps
10 to 13 hours for brain growth and memory
9 to 11 hours
8 to 10 hours. The body clock shifts later at this age
7 to 9 hours, or 5 to 6 full cycles
7 to 8 hours, with attention to sleep quality
Ranges follow the American Academy of Sleep Medicine and National Sleep Foundation guidance.
Yes. It is free to use and needs no sign up.
A normal alarm wakes you at a fixed time, even in deep sleep. This calculator suggests a bedtime so you wake at the end of a full sleep cycle, which usually means less morning grogginess.
Enter the Fajr time as your wake up time. You will see bedtimes that let you wake at the end of a full cycle before the call to prayer. Five cycles, about 7.5 hours, is a good target for most adults.
Most adults do well with five to six cycles, which is 7.5 to 9 hours. Cycle length varies from person to person, so these times are estimates and not medical advice.
Most people take a few minutes to drift off. The calculator assumes 15 minutes, and you can change it to match your own routine.
More tools and guides