Sleep by age
How much sleep does an adult need?
Adults should sleep seven or more hours a night. Note the shape of that: it is a floor rather than a target, and it is phrased that way on purpose because the evidence for the bottom edge is much stronger than for any ideal number.
In short
The American Academy of Sleep Medicine recommends that adults sleep 7 or more hours per night on a regular basis to promote optimal health. It is expressed as a minimum rather than a range because the evidence supports a lower bound far more firmly than it supports an ideal figure.
- Hours per night
- 7+Hours per nightAASM adult consensus, 2015
- Sleep cycles, roughly
- 5Sleep cycles, roughlySeven and a half hours
- To fall asleep
- 15 minTo fall asleepBed time is not sleep time
Adults, 18 to 60 years
7 to 9hours per night
As published by the American Academy of Sleep Medicine in its consensus statement on recommended sleep duration. Quoted as a range because that is how it was issued: healthy sleepers in this band sit across the whole span, and a single number would be us inventing a precision the evidence does not have.
Why it is a floor and not a range
The adult consensus is phrased as seven or more, which is unusual for a health recommendation and is the most informative thing about it. The panel found the evidence for harm below seven hours considerably stronger than the evidence for any specific optimum above it, so they gave the boundary they could defend rather than the target people wanted.
The practical reading is that the useful question is not whether you are hitting an ideal number. It is whether you are consistently under the floor, because that is the part the evidence is actually clear about.
The figure is from the AASM and Sleep Research Society adult consensus published in 2015.
Time in bed is not time asleep
Eight hours between the light going off and the alarm is not eight hours of sleep. It takes most people around fifteen minutes to fall asleep, and almost everybody wakes several times a night without forming a memory of it. Both of those come out of the total, and neither shows up in the mental arithmetic people do about their own sleep.
This is why the sensible way to hit seven hours is to allow closer to eight of opportunity. It is also why the number people report about themselves is usually higher than the number a measurement produces, in both directions but more often upward.
You stop noticing the deficit before you stop having it
The most awkward finding in this area is that self-rated alertness flattens out under chronic short sleep while measured performance keeps declining. Which means the sensation of having adapted to six hours is exactly what the process of not adapting to six hours feels like from the inside.
That is the whole case for measuring rather than estimating, and it is a modest case rather than a dramatic one: a number from a phone is an estimate too. It is simply a better instrument than a memory of how last night felt.
What an estimate from a phone is and is not: /blog/what-estimated-sleep-stages-really-mean.
The hours are not the only variable
Two people both getting seven and a half hours can have quite different nights, because when you sleep and how steadily you do it both matter. A schedule that moves by two hours across a week gives the body clock nothing to settle into, and that shows up as difficulty falling asleep and difficulty waking, which is the pair of symptoms people usually try to fix with more hours.
The other variable is where the alarm lands. Seven and a half hours ending mid-cycle feels worse than seven and a quarter ending on a boundary, which is arithmetic you can do at /sleep-at and physiology you can read at /guides/what-is-sleep-inertia.
What is actually different at this age
The total is the headline. These are the things that change underneath it, and they are usually what somebody is really asking about.
What changes
- The requirement flattens out in adulthood, so there is no meaningful difference between what a 25 year old and a 45 year old need.
- Your ability to judge your own impairment from short sleep degrades before your performance does, so self-assessment stops being reliable.
- The gap between time in bed and time asleep becomes the thing that quietly eats the total, because nobody budgets for it.
Where an app stops being the right tool
Stated plainly rather than buried, because a sleep app writing about sleep has an obvious incentive not to.
Limits worth knowing
- Sleep stages on a phone-only night are estimates, not measurements. Anything staging your sleep from a microphone and an accelerometer is inferring, and Tock says so.
- A sleep app cannot tell you why you are short, only that you are. The causes worth ruling out are medical and belong with a doctor.
- Seven hours is a population figure. It is not a personal prescription, and a small number of people genuinely need more or less.
Tock estimates sleep and is not a medical device. Nothing here is medical advice, a diagnosis, or a substitute for one. If sleep is genuinely not working, that is a conversation for a doctor rather than for an app or an article.
Questions people ask
How many hours of sleep do adults need?
Seven or more per night, according to the American Academy of Sleep Medicine. It is stated as a minimum rather than a range because the evidence for harm below seven hours is much stronger than the evidence for any particular ideal number above it.
Is 6 hours of sleep enough?
It is below the recommended floor. A small number of people genuinely function well on six, and that number is far smaller than the number who believe they are in it, because self-assessed alertness stops tracking measured performance under chronic short sleep.
Is 9 hours of sleep too much?
Not inherently. The adult recommendation is a lower bound, so nine hours is not a violation of it. Consistently needing much more than nine to feel functional is worth mentioning to a doctor, because it can point at something other than sleep duration.
How much sleep do I need if I exercise a lot?
The consensus figure does not vary by training load, and the honest answer is that the evidence for a specific higher number is thin. What is clear is that the floor does not move down, so heavy training is a reason to protect seven or more hours rather than a reason to expect to need less.
Other age bands
The same consensus statement, read for a different age.
- How much sleep teenagers needThe American Academy of Sleep Medicine recommends that teenagers aged 13 to 18 years sleep 8 to 10 hours per 24 hours on a regular basis. The obstacle is a genuine biological shift: the adolescent circadian rhythm runs later, so a teenager cannot reliably fall asleep at the time an early school start requires.
- How much sleep older adults needThe American Academy of Sleep Medicine recommendation of 7 or more hours per night applies to adults without an upper age cut-off. What changes with age is not how much sleep is needed but how easily it is obtained: the night becomes lighter, more broken, and shifts earlier.
Elsewhere on the site
A different corner of the same problem.
- RoundupsThe best alarm apps for heavy sleepersTock is the best alarm app for heavy sleepers: it rings on AlarmKit, so it gets through silent mode and a Focus, and it keeps ringing until you finish a small task. Alarmy is the real rival and the better pick if you want the widest set of dismissal tasks or a free tier to test the idea on.
- Wake timesWaking up at 6:30amBedtimes by sleep cycle for a 6:30am alarm.
- BedtimesGoing to bed at 10:30pmWhere to put the alarm after a 10:30pm lights-out.
- NapsThe 10 minute napA 10 minute nap lifts alertness without taking you into slow wave sleep, so you wake up clear rather than groggy. It is the safest nap to take close to work or driving, and it does nothing for memory consolidation, which needs considerably longer.
- Wake tonesCustom alarm soundTock comes with 18 wake tones, and if none of them suit you it takes your own audio as the alarm instead. Whatever you choose still gets scheduled through Apple's AlarmKit, so the silent switch, an active Focus and a fully closed app have no bearing on whether it rings.
- Head to headApple Health Sleep vs PillowApple's built-in tracking is enough if you want hours and stages and nothing more. Pillow is for the Watch wearer who finds Apple's presentation too thin and wants the night detected and shaped for them without pressing anything.
Knowing the number is the easy half
Hitting it is the other one. Tock measures what you actually got rather than what the schedule allowed for, and wakes you at a lighter moment inside the last half hour.