Sleep calculator
Sleep calculator: when to go to bed and when to wake up
Adults need at least 7 hours of sleep a night on a regular basis. Enter when you need to wake up to see when to go to bed, including the time it takes to fall asleep.
Plan your sleep
The time to fall asleep starts at 15 minutes; change it if you know how long you usually take.
Example: waking at 06:30, 15 minutes to fall asleep
9 hours
21:15
8 hours
22:15
7.5 hours
22:45
7 hours
23:15
How much sleep you need
| Age | Recommended (NSF, 2015) |
|---|---|
| 14–17 | 8–10 hours |
| 18–25 | 7–9 hours |
| 26–64 | 7–9 hours |
| 65 and over | 7–8 hours |
The American Academy of Sleep Medicine and the Sleep Research Society agree that adults should sleep 7 hours or more a night regularly. Some people need more, especially after illness, hard training or a run of short nights.
Sleep cycles: useful, but not exact
Sleep runs in cycles of light, deep and REM sleep that last about 90 minutes on average, so 7.5 hours is about five cycles. Real cycles vary: the first usually lasts 70 to 100 minutes and later ones 90 to 120, so no calculator can time your wake-up to the end of a cycle. Aim for enough total sleep and a steady schedule; an alarm that wakes you mid-cycle now and then does far less harm than a short night.
Regularity matters as much as hours
In a 2024 study of about 61,000 UK Biobank participants who wore activity trackers, those with the most regular sleep timing had a lower risk of death over the following years than those with the least regular sleep, and regularity predicted it better than sleep duration did. It is an association, not proof of cause, but it fits a wider body of research: going to bed and waking up at similar times, weekends included, is worth the effort.
A better night, step by step
- Keep caffeine well before bed: the caffeine calculator shows how much is left at bedtime.
- Get daylight in the morning and dim screens and lights in the last hour.
- Keep the bedroom cool, dark and quiet.
- If you snore loudly, stop breathing at night or feel sleepy despite enough hours, talk to a doctor: a sleep tracker can’t rule out a sleep disorder.
Sleep in Bodyvault
Bodyvault’s Sleep score compares last night with your own sleep need and how regular your timing is, and a wind-down reminder adapts to when you actually fall asleep. Read how Apple’s own score works in Apple Watch sleep score, and how sleep feeds the Readiness score.
Privacy
The calculation runs in this page. Nothing you type is sent to a server, saved in your browser or put into the address bar; reloading the page restores the example. The site’s usual behaviour is in the privacy policy.
Questions
What time should I go to bed to wake up at 6:30?
For 7.5 hours of sleep with 15 minutes to fall asleep, at 22:45. For 8 hours, at 22:15.
Is it better to sleep in 90-minute cycles?
Cycles average about 90 minutes but vary a lot, so timing sleep to cycles is approximate at best. Total sleep and a regular schedule matter more.
How much sleep do adults need?
At least 7 hours a night regularly (AASM and Sleep Research Society); 7–9 hours for adults up to 64 and 7–8 hours from 65 (National Sleep Foundation).
Is my data saved?
No. The calculation runs in the page and nothing is sent anywhere.
Sources
- Watson NF et al. (2015). Recommended amount of sleep for a healthy adult: a joint consensus statement of the AASM and Sleep Research Society. Sleep 38(6):843–844.
- Hirshkowitz M et al. (2015). National Sleep Foundation’s sleep time duration recommendations: methodology and results summary. Sleep Health 1(1):40–43.
- Institute of Medicine (2006). Sleep Disorders and Sleep Deprivation: An Unmet Public Health Problem, chapter 2, Sleep physiology.
- Windred DP et al. (2024). Sleep regularity is a stronger predictor of mortality risk than sleep duration: a prospective cohort study. Sleep 47(1):zsad253.