Bedtimes
You are going to bed at 12:30am. When should the alarm be?
Half past midnight is a normal bedtime for a genuinely late body clock and a problem for everyone else, and the useful question is which of those you are rather than whether the hour is respectable.
In short
If you go to bed at 12:30am, set your alarm for 8:15am. That is 7h 30m of sleep across 5 full cycles, plus the fifteen minutes it takes most people to actually fall asleep, so you wake at the end of a cycle rather than inside one. 9:45am gives you 9h and 6:45am still leaves you 6h.
- Alarm for a full night
- 8:15amAlarm for a full night5 cycles, 7h 30m asleep
- Length of an average sleep cycle
- 90 minLength of an average sleep cycleReal ones run 70 to 120
- Added before the first cycle
- 0h 15mAdded before the first cycleMost calculators forget this
| Cycles | Set the alarm | Time asleep | What it is good for |
|---|---|---|---|
| 6 | 9:45am | 9h | Nine hours. Worth it if you are paying back debt, and more than most adults need every night. |
| 5 | 8:15amAim here | 7h 30m | The target most adults should hold on a normal week. |
| 4 | 6:45am | 6h | Six hours. Short, but a whole number of cycles, so you surface from a lighter patch. |
| 3 | 5:15am | 4h 30m | An emergency night. Fine occasionally, damaging as a pattern. |
Late by clock or late by circumstance
Two different people end up here. One has always been like this: sleepy around one, sharp in the evening, hopeless before nine, and was the same at fourteen. The other used to go to bed at eleven and has drifted, usually because of shift patterns, a new baby, a phone, or a run of stress that made lying in the dark unappealing.
The distinction matters because the fix is different. A late chronotype needs the schedule built around it wherever possible and shifted with light where it cannot be. Drift needs the drift addressed, and it usually reverses much faster than people expect once the mornings become consistent.
- From 12:30am, five cycles lands at 9:15am and four at 7:45am
- Always been late points to chronotype; became late points to drift
- Drift usually responds within a week or two, a chronotype takes longer and moves less
What to do when the alarm cannot move
If your morning is fixed and your body wants half past midnight, you are running a short night whatever anybody advises. Under those conditions the things worth spending effort on change: total sleep is largely out of your hands, so consistency, the darkness of the room, and which part of a cycle the alarm lands in are what is left.
The last of those is the one with an immediate answer. An alarm that waits for a lighter moment inside the half hour before your set time does not add sleep, and it does change how the sleep you got is handed back to you.
What sleep inertia is and why the timing matters more than the total is at /guides/what-is-sleep-inertia.
The table is an average, and your night is not
Ninety minutes is the number everybody quotes because it is roughly the mean. A real night does not run to it. Your first cycle tends to be short, the middle ones stretch, and by the last couple of hours you are cycling faster with more of each one spent in light sleep and REM. So the arithmetic above gets you to approximately the right alarm, and then the last half hour is a coin toss.
That coin toss is the entire argument for a smart alarm, and it is why this page ends with one rather than with a schedule. Tock spends the thirty minutes before 8:15am watching for the moment you are already stirring, on two channels: movement from the accelerometer and sound from the microphone. When it finds one it rings a little early. When it does not,8:15am rings exactly as you set it, so the fallback is never worse than a normal alarm. You can read the mechanism at how smart wake works, or start with sleep cycles explained if the arithmetic itself is the part you want to understand properly.
Questions people ask
If I go to bed at 12:30am what time should I wake up?
Five sleep cycles puts the alarm at 9:15am for seven and a half hours of sleep. Four cycles is 7:45am at six hours, and three is 6:15am at four and a half. Each includes about fifteen minutes to fall asleep.
How much sleep is 12:30am to 7am?
Six and a half hours in bed and around six and a quarter asleep. That is between four and five cycles, so the alarm is likely to land inside one, and it is below the seven hour adult figure.
Can I train myself to go to bed earlier than 12:30am?
Usually yes, by fifteen to thirty minutes at a time rather than in one jump, and by moving the morning first. Hold a fixed wake time, get bright light soon after it, and keep the last ninety minutes before bed dim. How far it moves depends on whether you are late by chronotype or late by drift.
Other bedtimes
The same arithmetic, run from a different lights-out.
- Going to bed at 8:00pmWhere to put the alarm after a 8:00pm lights-out.
- Going to bed at 8:30pmWhere to put the alarm after a 8:30pm lights-out.
- Going to bed at 9:00pmWhere to put the alarm after a 9:00pm lights-out.
- Going to bed at 9:30pmWhere to put the alarm after a 9:30pm lights-out.
- Going to bed at 10:00pmWhere to put the alarm after a 10:00pm lights-out.
- Going to bed at 10:30pmWhere to put the alarm after a 10:30pm lights-out.
- Going to bed at 11:00pmWhere to put the alarm after a 11:00pm lights-out.
- Going to bed at 11:30pmWhere to put the alarm after a 11:30pm lights-out.
- Going to bed at 12:00amWhere to put the alarm after a 12:00am lights-out.
- Going to bed at 1:00amWhere to put the alarm after a 1:00am lights-out.
- Going to bed at 1:30amWhere to put the alarm after a 1:30am lights-out.
- Going to bed at 2:00amWhere to put the alarm after a 2:00am lights-out.
- Going to bed at 3:00amWhere to put the alarm after a 3:00am lights-out.
Elsewhere on the site
A different corner of the same problem.
- Tock for youPeople who hate morningsThe alarm goes off and you feel physically wrong. Not tired exactly, more like you were pulled out of something, and it takes the better part of an hour before you are a person again.
- AlternativesTock vs PzizzKeep Pzizz if you nap, or if your mind needs words to hold onto while you fall asleep. Tock generates its sound too, but it has no voiceover and nothing for naps. What Tock adds is the alarm, the tracking and the morning report Pzizz does not attempt.
- RoundupsThe best sleep apps for studentsFor most students the best answer is free: the iPhone Clock app, a wake time you keep at weekends, and Alarmy's free tier if you sleep through things. Tock is the paid pick worth the money once you have tried that and still miss 9am lectures.
- Wake timesWaking up at 7:30amBedtimes by sleep cycle for a 7:30am alarm.
- Sleep by ageHow 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.
- NapsThe 60 minute napA 60 minute nap includes a substantial amount of slow wave sleep, which is useful for recovery and for some kinds of memory, and it usually ends before the cycle completes. That means the benefit is real and the wake-up is often groggy, so it suits situations where the hour afterwards is flexible.
Tomorrow, you wake up just before your alarm
Setting the alarm on a cycle boundary is arithmetic and your night is not. Tock watches the half hour before 8:15am for a lighter moment and rings then, and your set time is always the fallback.