How much sleep do you need?
How much sleep you need, and how to work out your bedtime from your alarm.
Most adults need at least 7 hours of sleep a night 12. To get 7 hours of sleep, give yourself about 8 hours in bed, because you won't be asleep the whole time you're there. So to work out your bedtime, start from your alarm and count back 8 hours. With a 6:30 alarm, that's bed around 10:30.
Is 6 hours of sleep enough?
Six hours a night is less than most adults need. People who regularly sleep less than 7 hours tend to make more mistakes and have more accidents 2.
Short nights also pile up in a way that's hard to feel. In a sleep lab, healthy adults in their twenties and thirties who got 6 hours or less in bed a night for two weeks ended up doing as badly on mental tests as people kept awake for up to two nights straight. When they were asked how sleepy they felt, they seemed largely unaware of how far they'd slipped 3. So count the hours instead of going by how you feel.
One bad night doesn't need a fix. Get up at your usual time the next morning and go about your day as normal.
Why time in bed isn't the same as time asleep
Take a night in bed from 11 to 7. It takes you a while to drop off and you're up for a bit around 3, so by the time your alarm goes off you've slept a little under 7 and a half hours. Get into bed at midnight instead and it's more like 6 and a half, though you'd probably still tell someone you got 7.
People tend to think they sleep longer than they do, too. Middle-aged adults who wore a sleep monitor on their wrist slept about 6 hours a night on average, but when they were asked, they said almost 7 4. So you might be getting less sleep than you think, and the full 8 hours in bed leaves room for that.
What time to go to bed for your alarm
Start with the time you have to get up, because that's usually the part of your day you can't move. Work or the school run decides it for you. Get up at about the same time on weekends too 5, within an hour or so, even after a late night.
If you're used to getting into bed at midnight, you probably won't fall asleep at 10:30 just because you decided to. Move your bedtime earlier by about 15 minutes every two or three nights, which gets you from midnight to 10:30 in about two weeks, a bit more if you go slower. I'd leave your weekday alarm where it is the whole time, even on the mornings you're tired. And if your only quiet time is late in the evening, going 15 minutes at a time means you're not giving all of it up at once.
Some nights you'll get into bed and be wide awake. Give it about 20 minutes, and if you're still awake after that, get up and do something quiet in low light, away from your phone 5. Go back to bed once you feel sleepy, and not before 5.
You might be a few weeks in and still not falling asleep until long after your new bedtime. That can mean your body clock is running late, so check whether you're a natural night owl before you push your bedtime any earlier.
When to see a doctor
See a doctor if you're giving yourself about 8 hours in bed and you still wake up tired most days or fight to stay awake in the afternoon 1.
Frequent loud snoring, gasping for air or breathing that stops and starts in your sleep can be signs of sleep apnea, and they're worth telling your doctor about 6. You might not know you're doing any of it until someone who sleeps near you tells you 6.
How much sleep you need at every age
These are the CDC's numbers, in hours a day 1.
| Age | Sleep each day |
|---|---|
| Newborns, 0 to 3 months | 14 to 17 hours |
| Babies, 4 to 12 months | 12 to 16 hours, including naps |
| Toddlers, 1 to 2 years | 11 to 14 hours, including naps |
| Preschool, 3 to 5 years | 10 to 13 hours, including naps |
| School age, 6 to 12 years | 9 to 12 hours |
| Teens, 13 to 17 years | 8 to 10 hours |
| Adults, 18 to 60 years | 7 or more hours |
| Adults, 61 to 64 years | 7 to 9 hours |
| Adults, 65 and older | 7 to 8 hours |
Teenagers need 8 to 10 hours 1, so if your teen is up at 7 for school, they need to be asleep by 11 just to get the low end of that.
Some adults need more than 7, too. Sleeping more than 9 hours a night can be right for young adults, for people who are sick and for anyone catching up after a stretch of short nights 2.
Turn this into a plan for your day.
Answer a few questions about your schedule and light access, and Calibrate builds a daily light-timing plan around the day you actually live.
References
- U.S. Centers for Disease Control and Prevention (2024). About sleep. U.S. Department of Health and Human Services; May 15, 2024; accessed October 12, 2026. www.cdc.gov/sleep/about/index.html
- Watson NF, Badr MS, Belenky G, et al. (2015). Recommended amount of sleep for a healthy adult: a joint consensus statement of the American Academy of Sleep Medicine and Sleep Research Society. J Clin Sleep Med 11(6):591-592. doi.org/10.5664/jcsm.4758
- Van Dongen HP, Maislin G, Mullington JM, Dinges DF (2003). The cumulative cost of additional wakefulness: dose-response effects on neurobehavioral functions and sleep physiology from chronic sleep restriction and total sleep deprivation. Sleep 26(2):117-126. doi.org/10.1093/sleep/26.2.117
- Lauderdale DS, Knutson KL, Yan LL, Liu K, Rathouz PJ (2008). Self-reported and measured sleep duration: how similar are they? Epidemiology 19(6):838-845. doi.org/10.1097/EDE.0b013e318187a7b0
- American Academy of Sleep Medicine (2020). Healthy sleep habits. American Academy of Sleep Medicine, sleepeducation.org; updated August 2020; accessed October 12, 2026. sleepeducation.org/healthy-sleep/healthy-sleep-habits/
- National Heart, Lung, and Blood Institute (2025). Sleep apnea: symptoms. U.S. National Institutes of Health; updated January 9, 2025; accessed October 12, 2026. www.nhlbi.nih.gov/health/sleep-apnea/symptoms