Find a bedtime for the time you must wake up, or a wake-up time for when you go to bed, in whole sleep cycles.
To wake at 7:00 am after 5 sleep cycles and 15 minutes to fall asleep, go to bed at 11:15 pm. The page counts back from your wake-up time: the number of cycles times the cycle length, plus the minutes you need to fall asleep. Five 90-minute cycles are 7 hours 30 minutes, so 7:00 am minus 7 h 30 min minus 15 min is 11:15 pm. Six cycles are 9 hours, which gives 9:45 pm. Going the other way, if you get into bed at 11:00 pm, 5 cycles plus 15 minutes to fall asleep end at 6:45 am, and 6 cycles end at 8:15 am. The table lists 3 to 10 cycles, from 4 h 30 min up to 15 h of sleep, so you can see every option, and the suggested times at the top are the ones whose sleep time falls in the recommended range for your age.
The recommended hours come from published consensus statements. The American Academy of Sleep Medicine recommends 9 to 12 hours for ages 6 to 12 and 8 to 10 hours for ages 13 to 18. For adults the AASM and the Sleep Research Society say 7 or more hours a night. The National Sleep Foundation gives 7 to 9 hours for adults and 7 to 8 for people of 65 and over. The page marks each row as shorter than, inside or longer than the range for the age group you choose. Children under 6 are not offered: the AASM ranges for babies and young children (for example 12 to 16 hours at 4 to 12 months) are per 24 hours including naps, so they cannot be checked against one night's sleep. Nothing here is a diagnosis, and individual needs differ.
The 90-minute cycle is an average, not a rule. Real cycles differ between people and through the night, so the page lets you change the cycle length from 60 to 120 minutes. With 100-minute cycles, 5 cycles are 8 h 20 min instead of 7 h 30 min. Waking in the middle of a cycle is not harmful, and many people feel fine a few minutes either side of the time shown. The time to fall asleep can be 0 to 120 minutes; if you take 30 minutes, each bedtime moves 15 minutes earlier than with the 15-minute default. Use the number you actually notice, not an ideal one.
This is arithmetic on a clock. It does not measure your sleep, detect sleep disorders or adjust for shift work, naps (it is not meant for babies or children under 6), caffeine, alcohol or medication. It cannot say that a certain cycle count will leave you refreshed. If you are tired most days after enough sleep, snore loudly or stop breathing in your sleep, talk to a doctor. Times wrap past midnight, so a bedtime of 2:15 am is shown as 2:15 am without a date. You can switch to a 24-hour clock. Nothing you type is stored or sent.
For a 7:00 am alarm, 5 cycles of 90 minutes plus 15 minutes to fall asleep gives 11:15 pm, and 6 cycles gives 9:45 pm. Both give a sleep time of 7.5 or 9 hours, inside the 7 to 9 hour range for adults.
With 15 minutes to fall asleep, 5 cycles end at 6:45 am and 6 cycles end at 8:15 am. Switch to Go to bed at, type 23:00 or 11:00 pm, and the table shows the other cycle counts too.
About 90 minutes is the figure the page starts with, but it is an average and yours can differ. Change Sleep cycle to any number from 60 to 120 minutes. At 100 minutes, 5 cycles are 8 h 20 min, so every time in the table moves.
Counting cycles starts when you are asleep, not when you lie down. Most people need some minutes to drift off, so the page adds them to the bedtime. Set Time to fall asleep to 0 if you fall asleep at once, or 30 if you take longer.
For adults the AASM and Sleep Research Society say 7 or more hours, and the National Sleep Foundation gives 7 to 9, or 7 to 8 from age 65. Teenagers of 13 to 18 are given 8 to 10 hours by the AASM, and children of 6 to 12 get 9 to 12. Pick your age group to see the range.
No. The text is processed in your browser and not uploaded, and this page does not save your times, so a refresh brings back the example.