Sleep calculator
Going to bed at 12:00 AM? Here's when to wake up
Lights off at 12:00 AM, about 15 minutes to fall asleep, then whole 90-minute cycles. The best alarm times are 7:45 AM or 9:15 AM. Here's the full table, and what each common alarm time actually leaves you with.
Wake-up times that end on a full cycle
| Wake up at | Cycles | Time asleep | Verdict |
|---|---|---|---|
| 4:45 AM set alarm | 3 | 4h 30m | Emergency only |
| 6:15 AM set alarm | 4 | 6h | Short, but workable now and then |
| 7:45 AM set alarm | 5 | 7h 30m | Recommended |
| 9:15 AM set alarm | 6 | 9h | Recommended |
The two recommended rows are where most adults do best. Anything under five cycles is a deficit you will repay later in the week, and three cycles is the kind of night you should only have on purpose.
How much sleep each alarm time gives you from 12:00 AM
The other direction: if your alarm is already fixed by work or school, here is what a 12:00 AM bedtime actually leaves you with.
| Alarm set for | You sleep about | How that lands |
|---|---|---|
| 5:00 AM | 4h 45m | Under-slept; expect a hard morning |
| 5:30 AM | 5h 15m | Under-slept; expect a hard morning |
| 6:00 AM | 5h 45m | Under-slept; expect a hard morning |
| 6:30 AM | 6h 15m | Under-slept; expect a hard morning |
| 7:00 AM | 6h 45m | Slightly short — fine occasionally |
| 7:30 AM | 7h 15m | Slightly short — fine occasionally |
| 8:00 AM | 7h 45m | A full night for most adults |
| 9:00 AM | 8h 45m | A full night for most adults |
These are averages, not rules — real cycles run anywhere from 80 to 110 minutes and get shorter through the night. Use the times as good starting points, and if you consistently wake exhausted on enough hours, that's worth raising with a doctor rather than a calculator.
After midnight, the question changes from when to wake up to whether you can
Going to bed at midnight or later is fine if the morning is free to move with it: six cycles from 12:30 AM is 9:45, which a remote worker or a student with a late timetable can live with. The trouble starts when the bedtime is late but the alarm is not. From 1 AM, a 7 o'clock alarm gives you under four cycles, and the table above says so in plain numbers.
That is the situation where people reach for more alarms, louder alarms and five snoozes, and none of it works, because the problem is not the alarm — it is that you are being woken from the deepest part of a short night. A body four cycles in will defend its sleep: it can find the phone, stop the alarm and go back under without creating a memory. That is why "I slept through it" and "I turned it off in my sleep" are so often the same event, and why you need to read why you turn off alarms in your sleep if the late nights are not going anywhere.
If you genuinely cannot move the bedtime — shift work, a newborn, a deadline — then the one thing that still works is separating the alarm from its off switch, so that stopping it requires standing up. A short night is survivable. A short night you sleep through is not.
Picking the time is the easy half
A wake time that ends on a cycle makes the first minute easier. It does not make the decision for you. If you sleep through alarms or turn them off without remembering, the right time on the clock changes nothing, because the off button is still within reach.
WakeUpBroo fixes that half. It rings on your iPhone with no snooze and no dismiss button; to stop it you read a rotating code from wakeupbroo.com/code on a laptop or other device you left across the room. By the time you've walked over and typed it, the wake-up has actually happened.
Other bedtimes
Turning in a little sooner? See the wake times for going to bed at 11:30 PM. Running later tonight? See going to bed at 12:30 AM. For any other time, use the sleep calculator, or start from the alarm instead with the online alarm clock.
FAQ
Frequently asked questions
If I go to bed at 12:00 AM, what time should I wake up?
Going to bed at 12:00 AM and allowing about 15 minutes to fall asleep, six full sleep cycles end at 9:15 AM and five end at 7:45 AM. Either gives most adults a full night; pick the one that fits your morning and set the alarm for exactly that time.
Is 12:00 AM a good bedtime?
It depends entirely on when you have to get up. 12:00 AM works if your wake time can sit at 7:45 AM or later. Paired with a 6 or 7 AM alarm it leaves you well short of a full night, and short nights are the ones people sleep through.
What if I don't fall asleep within 15 minutes?
Then shift the table by however long you actually take. If it is routinely 45 minutes, add 30 to every wake time above — or, better, go to bed when you are sleepy rather than when the clock says, and hold the wake time fixed instead.
I set the right alarm and still sleep through it. Now what?
That is the half a calculator cannot solve. If you dismiss alarms half-asleep, you need one that cannot be stopped from bed. WakeUpBroo for iPhone has no snooze and no dismiss button — the alarm stops only when you type a rotating code from wakeupbroo.com/code on a device across the room.
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Picked a wake-up time? Make it stick.
Knowing when to wake up doesn't get you out of bed. WakeUpBroo has no snooze and no dismiss button — the alarm stops only when you read a rotating code from this website on another device. Free to download, 7-day free trial.
Free on iPhone · Android in development