Sleep Calculator

Find a bedtime or wake-up time that ends on a whole sleep cycle, with the hours recommended for your age.

Calculate from

Age

Sets the recommended hours.

Wake-up time

Sleep cycle (minutes)

Falling asleep (minutes)

Go to bed at

21:45
6 cycles, 9 hours asleep
9 hours and 15 minutes in bed
Within the recommended hours
23:15
5 cycles, 7 hours and 30 minutes asleep
7 hours and 45 minutes in bed
Within the recommended hours
00:45
4 cycles, 6 hours asleep
6 hours and 15 minutes in bed

Recommended at 18–60 years: 7 hours or more (AASM and SRS, Watson 2015).

Gives bedtimes that end on a whole number of sleep cycles at the time you need to wake, or wake-up times from a bedtime or from now, with the hours asleep and in bed for each. It marks the options within the hours recommended for your age, and lets you set the cycle length and the time you take to fall asleep. Every calculation runs in your browser.

How to use it

Wake up at gives bedtimes, Go to bed at wake-up times, and Sleep now wake-up times from your device's clock, which a shared link does not carry. Each gives 6, 5 and 4 cycles. The sleep cycle is 90 minutes unless you set it, from 70 to 120; falling asleep is 15 minutes, from 0 to 60. Age sets the recommended hours and follows the age saved by the other health tools until you choose one. Under 13 it gives the recommended hours only.

How it works

Sleep runs in cycles of non-REM and REM sleep. The first cycle of the night lasts 70 to 100 minutes on average and later ones about 90 to 120, so the usual 90 minutes is a rough guide, and the cycle length here can be changed. A bedtime is the wake-up time less the cycles and the time to fall asleep; a wake-up time is the bedtime plus both, past midnight where it runs over. A change of clocks for daylight saving overnight is not allowed for.

An option is marked as within the recommended hours when its time asleep is at least the minimum for your age and no more than the maximum, where the source sets one.

Bedtime = wake-up time − (cycles × cycle length + time to fall asleep)

Wake-up time = bedtime + time to fall asleep + cycles × cycle length

Examples

Waking at 07:00, as an adult

With the default options, the bedtimes for 6, 5 and 4 cycles are 21:45, 23:15, 00:45. 6 cycles (9 hours) and 5 cycles (7 hours and 30 minutes) are within 7 hours or more, recommended at 18–60 years.

Going to bed at 22:30, aged 65 or over

The wake-up times are 07:45, 06:15, 04:45. 5 cycles (7 hours and 30 minutes) is within 7–8 hours, recommended at 65 and over.

Recommended sleep by age

Hours of sleep in 24 hours, one source per age band

Age	Hours	Source
4–12 months	12–16 hours, naps included	AASM, Paruthi 2016
1–2 years	11–14 hours, naps included	AASM, Paruthi 2016
3–5 years	10–13 hours, naps included	AASM, Paruthi 2016
6–12 years	9–12 hours	AASM, Paruthi 2016
13–17 years	8–10 hours	AASM, Paruthi 2016
18–60 years	7 hours or more	AASM and SRS, Watson 2015
61–64 years	7–9 hours	National Sleep Foundation, Hirshkowitz 2015
65 and over	7–8 hours	National Sleep Foundation, Hirshkowitz 2015

Rules and sources

Children's hours are the American Academy of Sleep Medicine's 2016 consensus, which runs to 18; here 18 counts as an adult. Adults to 60 take the 2015 AASM and Sleep Research Society statement, 7 hours or more, which sets no maximum. From 61 the bands are the National Sleep Foundation's 2015 recommendations, 7–9 hours to 64 and 7–8 hours from 65. Cycle times use an adult's cycle, so they start at 13.

Sources

Paruthi S et al. Recommended amount of sleep for pediatric populations: a consensus statement of the American Academy of Sleep Medicine (J Clin Sleep Med 2016;12(6):785–786) — American Academy of Sleep Medicine
Watson NF et al. Recommended amount of sleep for a healthy adult: a joint consensus statement of the American Academy of Sleep Medicine and Sleep Research Society (Sleep 2015;38(6):843–844) — American Academy of Sleep Medicine and Sleep Research Society
Hirshkowitz M et al. National Sleep Foundation's sleep time duration recommendations: methodology and results summary (Sleep Health 2015;1(1):40–43) — National Sleep Foundation
Sleep Disorders and Sleep Deprivation: An Unmet Public Health Problem (2006), chapter 2, citing Carskadon and Dement (2005) — Institute of Medicine

Reviewed 20 October 2026

Frequently asked questions

It is widely said, but no trial was found showing that timing an alarm to the end of a cycle reduces grogginess. Cycles also vary in length, so a calculated time is only near the end of one. The hours you sleep in total are what the age recommendations measure.