Bedtimes
You know when you are going to bed. This is where the alarm goes
Every bedtime calculator on the internet runs this backwards: you tell it your alarm and it tells you when to go to bed. That is the wrong question at eleven at night, when the bedtime is already decided and the only thing still open is the alarm. These pages answer the version people actually have.
In short
Take the time the light goes off, add about fifteen minutes to fall asleep, then add 90 minutes for each full sleep cycle. Five cycles is seven and a half hours of sleep and is the target most adults should hold. Setting the alarm on a cycle boundary rather than on a round number is what stops you being pulled out of deep sleep.
- Average sleep cycle
- 90 minAverage sleep cycleReal ones run 70 to 120
- To fall asleep
- 15 minTo fall asleepAdded before cycle one
- Cycles most adults want
- 5Cycles most adults wantSeven and a half hours
Why this is a different question from the one every calculator answers
There are two ways to ask about sleep timing and they belong to two different people. One has an alarm they did not choose, usually set by a job or a school run, and needs to know when to turn the light off. That reader is served bythe wake time pages, which count backwards.
The other is already in bed, or deciding whether to be, and the bedtime is the fixed end. For them, counting backwards from a hypothetical alarm is useless. What they need is the alarm itself, worked forwards from the hour they are actually at, which is what these pages do.
The arithmetic is not complicated and it is worth being explicit about it, because two of the three steps are where the popular versions go wrong. Whole cycles rather than round hours, so the alarm lands on a boundary. Fifteen minutes added at the start rather than assumed away, because nobody falls asleep on contact. And the honest caveat thatsleep architecture shifts across a night, so the ninety minute figure is a mean and not a promise.
Evening bedtimes
Eight until midnight, which is where almost everybody actually is. The earlier end suits a start before six; the later end starts costing a normal working morning.
- Bed at 8:00pmFive full cycles puts the alarm at 3:45am, which is 7h 30m of sleep.
- Bed at 8:30pmFive full cycles puts the alarm at 4:15am, which is 7h 30m of sleep.
- Bed at 9:00pmFive full cycles puts the alarm at 4:45am, which is 7h 30m of sleep.
- Bed at 9:30pmFive full cycles puts the alarm at 5:15am, which is 7h 30m of sleep.
- Bed at 10:00pmFive full cycles puts the alarm at 5:45am, which is 7h 30m of sleep.
- Bed at 10:30pmFive full cycles puts the alarm at 6:15am, which is 7h 30m of sleep.
- Bed at 11:00pmFive full cycles puts the alarm at 6:45am, which is 7h 30m of sleep.
- Bed at 11:30pmFive full cycles puts the alarm at 7:15am, which is 7h 30m of sleep.
After midnight
Late shifts, late chronotypes and nights that got away. Sleep taken across a morning is more fragile than the same hours at night, and these pages say why.
- Bed at 8:00pmFive full cycles puts the alarm at 3:45am, which is 7h 30m of sleep.
- Bed at 8:30pmFive full cycles puts the alarm at 4:15am, which is 7h 30m of sleep.
- Bed at 9:00pmFive full cycles puts the alarm at 4:45am, which is 7h 30m of sleep.
- Bed at 9:30pmFive full cycles puts the alarm at 5:15am, which is 7h 30m of sleep.
- Bed at 10:00pmFive full cycles puts the alarm at 5:45am, which is 7h 30m of sleep.
- Bed at 10:30pmFive full cycles puts the alarm at 6:15am, which is 7h 30m of sleep.
- Bed at 11:00pmFive full cycles puts the alarm at 6:45am, which is 7h 30m of sleep.
- Bed at 11:30pmFive full cycles puts the alarm at 7:15am, which is 7h 30m of sleep.
- Bed at 12:00amFive full cycles puts the alarm at 7:45am, which is 7h 30m of sleep.
- Bed at 12:30amFive full cycles puts the alarm at 8:15am, which is 7h 30m of sleep.
- Bed at 1:00amFive full cycles puts the alarm at 8:45am, which is 7h 30m of sleep.
- Bed at 1:30amFive full cycles puts the alarm at 9:15am, which is 7h 30m of sleep.
- Bed at 2:00amFive full cycles puts the alarm at 9:45am, which is 7h 30m of sleep.
- Bed at 3:00amFive full cycles puts the alarm at 10:45am, which is 7h 30m of sleep.
Questions people ask
How do I work out what time to wake up?
Start at the time the light actually goes off. Add about fifteen minutes for falling asleep, then add 90 minutes for each whole sleep cycle you want. Five cycles is seven and a half hours of sleep, which is the target most adults should hold on a normal week.
Why add fifteen minutes before the first cycle?
Because you are not asleep at the moment you get into bed. Most bedtime calculators quietly skip this and then tell you to go to bed at the time you would need to already be unconscious, which makes every night come in a quarter of an hour short. Fifteen minutes is an average and yours may differ.
Is it better to wake at the end of a sleep cycle?
Generally yes. Being woken out of deep sleep produces stronger sleep inertia, which is the grogginess that can last twenty minutes or more, than surfacing from a lighter stretch. That is why a whole number of cycles often beats a round number of hours, even when the round number is slightly more sleep.
How accurate is the 90 minute sleep cycle?
It is a useful average rather than a measurement. Real cycles run roughly 70 to 120 minutes and change length through the night, with the early ones carrying more deep sleep and the later ones more REM. That variability is precisely why an alarm that watches for a light moment beats one that trusts the arithmetic.
Elsewhere on the site
A different corner of the same problem.
- Head to headSleepScore vs SnoreLabIf snoring is the complaint and you want to find out whether the mouthguard made a difference, SnoreLab. If you want the whole night measured without wearing anything, SleepScore.
- FeaturesSleep scoreThe sleep score is a single number for a night, sitting at the top of that night detail view. Underneath it are the parts that produced it, and across nights the insights cover 21 metrics in 7 groups plus long-run measures like sleep regularity and sleep debt.
- Sleep soundsDistant stormFar-off thunder helps at the start of the night because the slow rolling swells give your attention something easy to follow while it lets go, and it hurts later because every roll is a change in level, which is exactly what surfaces a light sleeper. Tock treats it as a fall-asleep aid and fades it out after half an hour by default.
- Tock for youNew parentsYou do not wake up to an alarm any more, you wake up to a small person, three or four times, and then you have to be a functioning adult by seven. The night is not so much short as it is in pieces.
- AlternativesTock vs RiseChoose Rise if planning your day around energy peaks and a running sleep debt is what actually changes your behaviour. Choose Tock if you want the alarm itself to be smarter, the night recorded from the phone, and a coach that can talk about what it heard.
- RoundupsThe best sleep apps for iPhone, sorted by what you're fixingFor iPhone, the best sleep app depends on the problem. Tock is the best all-round pick when the alarm and the morning are what is broken, Apple Health Sleep is the free place to start, Calm is for people who cannot fall asleep, AutoSleep is for Apple Watch owners, Rise is for sleep debt and SnoreLab is for snoring.
The arithmetic gets you close. The last half hour is the problem
Tock spends the thirty minutes before your alarm watching for a lighter moment, on movement and on sound, and rings when it finds one. Your set time is always the fallback, so it is never worse than a normal alarm.