Sleep Cycle Bedtime Calculator
What time to go to bed or wake up: 3 to 7 whole 90-minute sleep cycles plus your minutes to fall asleep, counted from your alarm or bedtime. How it works
Use the Sleep Cycle Bedtime Calculator
About the Sleep Cycle Bedtime Calculator
To wake at 7:00 AM and take 15 minutes to fall asleep, go to bed at 11:15 PM for 5 sleep cycles (7 h 30 min) or at 9:45 PM for 6 cycles (9 h). The calculator counts back from a wake time, or forward from a bedtime, in whole 90-minute cycles from 3 to 7, plus a fall-asleep allowance of 5 to 30 minutes. The CDC recommends 7 or more hours for adults aged 18 to 60, so 5 cycles is the shortest night here that meets it.
Bedtimes for each wake time (15 minutes to fall asleep)
| Wake time | 3 cycles (4 h 30 min) | 4 cycles (6 h) | 5 cycles (7 h 30 min) | 6 cycles (9 h) | 7 cycles (10 h 30 min) |
|---|---|---|---|---|---|
| 6:00 AM | 1:15 AM | 11:45 PM (prev day) | 10:15 PM (prev day) | 8:45 PM (prev day) | 7:15 PM (prev day) |
| 6:30 AM | 1:45 AM | 12:15 AM | 10:45 PM (prev day) | 9:15 PM (prev day) | 7:45 PM (prev day) |
| 7:00 AM | 2:15 AM | 12:45 AM | 11:15 PM (prev day) | 9:45 PM (prev day) | 8:15 PM (prev day) |
| 7:30 AM | 2:45 AM | 1:15 AM | 11:45 PM (prev day) | 10:15 PM (prev day) | 8:45 PM (prev day) |
| 8:00 AM | 3:15 AM | 1:45 AM | 12:15 AM | 10:45 PM (prev day) | 9:15 PM (prev day) |
The cells are the bedtimes the calculator shows in 12-hour format, including its “(prev day)” note.
Wake times for each bedtime (15 minutes to fall asleep)
| Bedtime | 3 cycles | 4 cycles | 5 cycles | 6 cycles | 7 cycles |
|---|---|---|---|---|---|
| 9:30 PM | 2:15 AM (next day) | 3:45 AM (next day) | 5:15 AM (next day) | 6:45 AM (next day) | 8:15 AM (next day) |
| 10:00 PM | 2:45 AM (next day) | 4:15 AM (next day) | 5:45 AM (next day) | 7:15 AM (next day) | 8:45 AM (next day) |
| 11:00 PM | 3:45 AM (next day) | 5:15 AM (next day) | 6:45 AM (next day) | 8:15 AM (next day) | 9:45 AM (next day) |
| 12:00 AM | 4:45 AM | 6:15 AM | 7:45 AM | 9:15 AM | 10:45 AM |
Cycles are 90 minutes each, so 3 cycles is 4 h 30 min asleep and 7 cycles is 10 h 30 min.
How the fall-asleep allowance moves a 7:00 AM wake time
| Time to fall asleep | Bedtime for 5 cycles | Bedtime for 6 cycles |
|---|---|---|
| 5 min | 11:25 PM (prev day) | 9:55 PM (prev day) |
| 10 min | 11:20 PM (prev day) | 9:50 PM (prev day) |
| 15 min | 11:15 PM (prev day) | 9:45 PM (prev day) |
| 20 min | 11:10 PM (prev day) | 9:40 PM (prev day) |
| 30 min | 11:00 PM (prev day) | 9:30 PM (prev day) |
Each extra minute to fall asleep moves the bedtime one minute earlier.
The five rows and their labels on the page
| Cycles | Time asleep | Label |
|---|---|---|
| 3 | 4h 30m | Minimal |
| 4 | 6h 00m | Short |
| 5 | 7h 30m | Standard |
| 6 | 9h 00m | Full |
| 7 | 10h 30m | Extended |
The labels are this calculator’s names, not medical categories. The page marks Standard and Full with a star, and a column on wider screens compares each row with the CDC’s hours: 7 or more for adults aged 18 to 60, 8 to 10 for teens aged 13 to 17.
Methodology
From a wake time: bedtime = wake time − fall-asleep time − cycles × 90 minutes. From a bedtime: wake time = bedtime + fall-asleep time + cycles × 90 minutes. The fall-asleep time is 5, 10, 15, 20 or 30 minutes (15 by default) and the cycle count runs from 3 to 7. Times that land on a different calendar day from the one entered are marked (prev day) or (next day). Times can be shown in 12-hour or 24-hour format.
How to use this tool
- Choose By Wake Time to get bedtimes, or By Bedtime to get wake times.
- Enter the time. The defaults are 07:00 for a wake time and 23:00 for a bedtime.
- Pick the fall-asleep time closest to how long you usually lie awake (5, 10, 15, 20 or 30 minutes), and a 12-hour or 24-hour display.
- Read the five rows, and copy a time with the copy button beside it.
Frequently asked questions
- What time should I go to bed if I wake up at 7 AM?
- With 15 minutes to fall asleep: 11:15 PM for 5 cycles (7 h 30 min), 9:45 PM for 6 cycles (9 h), 12:45 AM for 4 cycles (6 h), 2:15 AM for 3 cycles and 8:15 PM for 7 cycles. If you take 30 minutes to fall asleep, 5 cycles moves to 11:00 PM and 6 cycles to 9:30 PM.
- What time should I wake up if I go to bed at 11 PM?
- With 15 minutes to fall asleep: 6:45 AM after 5 cycles, 8:15 AM after 6 cycles, 5:15 AM after 4 cycles, 3:45 AM after 3 and 9:45 AM after 7. All are on the next day.
- How does a 90-minute sleep cycle calculator work?
- It adds whole multiples of 90 minutes, and your fall-asleep time, to a bedtime, or subtracts them from a wake time. The idea is to have the alarm land at the end of a cycle. The calculator does not measure your sleep, so it cannot know where your own cycles end.
- Is every sleep cycle 90 minutes long?
- No. The Sleep Foundation says cycles average about 90 minutes, with the first often shorter, 70 to 100 minutes, and later ones usually 90 to 120. Length also varies with age and recent sleep. Treat the times as a schedule to try, not a prediction of when you will wake naturally.
- How many sleep cycles are in a night?
- The Sleep Foundation describes four to six cycles in a typical night. The calculator lists 3 to 7 so you can see short and long nights side by side.
- How many hours of sleep do I need?
- The CDC recommends 7 or more hours a night for adults aged 18 to 60, 7 to 9 hours at 61 to 64, 7 to 8 hours from 65, and 8 to 10 hours for teens aged 13 to 17. In cycles that means 3 (4 h 30 min) and 4 (6 h) are short nights for any adult, while 6 cycles (9 h) is the only row inside the teen range.
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