Sleep Calculator
Enter when you need to wake up and get bedtimes that fit whole 90-minute sleep cycles, or wake-up times if you go to bed now.
6:30 AM, 22:45 or 11pm
Your own usual time.
About 90 for most adults.
Times land at the end of a whole sleep cycle, after the minutes it takes you to fall asleep.
To wake at 6:30 AM, go to sleep at
9:15 PM or 10:45 PM
6 cycles (9 h 00 min) or 5 cycles (7 h 30 min) of sleep
| Go to sleep at | Cycles | Sleep |
|---|---|---|
| 9:15 PM | 6 | 9 h 00 min ✓ 7 h or more |
| 10:45 PM | 5 | 7 h 30 min ✓ 7 h or more |
| 12:15 AM | 4 | 6 h 00 min |
| 1:45 AM | 3 | 4 h 30 min |
What this page cannot tell you
Cycle length varies from person to person and through the night, so these times are a rough guide. This page cannot assess sleep problems; persistent trouble sleeping or daytime sleepiness is something to raise with a doctor.
How to use the sleep calculator
- Choose wake-up or bedtime. Which time you already know.
- Enter the time. For example 6:30 AM.
- Set minutes to fall asleep. Your own usual time.
- Read the times. Options for 6, 5, 4 and 3 full cycles.
10 times people use a sleep cycle calculator
Early work shifts
A nurse starting at 7 AM picks a bedtime that fits whole cycles.
Exam mornings
A student plans sleep before an early exam.
Early flights
A traveller times sleep before a 5 AM airport trip.
Shift workers
A night worker plans sleep after a shift.
Naps
Someone picks a nap length that ends at a cycle.
New parents
A parent times a stretch of sleep between feeds.
Jet lag
A traveller plans bedtimes in a new time zone.
School mornings
A parent works out a child's bedtime from the alarm time.
Weekend reset
Someone moves bedtime earlier before the work week.
Late nights
Someone going to bed late sees when a full cycle ends.
How the times are worked out
Bedtime = wake-up time − cycles × cycle length − minutes to fall asleep; wake-up time = bedtime + minutes to fall asleep + cycles × cycle length. The default cycle is 90 minutes: the National Institute of Neurological Disorders and Stroke says REM sleep first occurs about 90 minutes after falling asleep and that sleep cycles through the stages several times a night.
The CDC lists 7 or more hours of sleep for adults aged 18–60; options of 7 hours or more are marked.
Limits: cycle length varies between people and through the night, so the times are a rough guide. The page cannot assess sleep problems; persistent trouble sleeping or daytime sleepiness is something to raise with a doctor.
Frequently asked questions
What time should I go to bed to wake up at 6 AM?
With 15 minutes to fall asleep, 8:45 PM (6 cycles) or 10:15 PM (5 cycles).
How long is a sleep cycle?
About 90 minutes for many adults, varying through the night.
How much sleep do adults need?
The CDC lists 7 or more hours for adults 18–60.
Why wake at the end of a cycle?
Waking from lighter sleep at the end of a cycle is often described as easier than waking from deep sleep; the page only does the timing.
Can I change the cycle length?
Yes, enter any length from 60 to 120 minutes.
Does it work for naps?
The options shown are 3 to 6 cycles. For a nap, one cycle is about 90 minutes plus your time to fall asleep.
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