Set an alarm for 1:38 AM
A free online alarm that rings at 1:38AM. Start it, leave the tab open, and it will sound at 1:38 AM. No app, no account, nothing to install. The countdown below shows exactly how long is left.
What time should you go to bed to wake at 1:38AM?
Sleep runs in cycles of roughly 90 minutes, and waking at the end of a cycle feels easier than waking in the middle of one. Allowing about 14 minutes to fall asleep, these bedtimes line up with a 1:38 AM alarm:
| Go to bed at | Cycles | Sleep |
|---|---|---|
| 4:24 PM | 6 | 9.0 hours |
| 5:54 PM | 5 | 7.5 hours |
| 7:24 PM | 4 | 6.0 hours |
Cycle length varies between people, so treat these as a guide rather than a prescription.
Who sets a 1:38AM alarm
Alarms in the small hours mostly serve night shifts, long drives and overnight processes. Waking in this window usually cuts into deep sleep, so if the alarm is a one-off, going to bed earlier matters more than it would for a normal morning.
If you go to bed now, when should the alarm ring?
Read the table the other way round when the bedtime is fixed rather than the wake time. Starting from a 1:38 AM alarm, these are the sleep totals you get for each bedtime:
| Sleep wanted | Bedtime | Cycles |
|---|---|---|
| 9 hours | 4:24 PM | 6 |
| 7.5 hours | 5:54 PM | 5 |
| 6 hours | 7:24 PM | 4 |
| 4.5 hours | 8:54 PM | 3 |
How the alarm works
The timer reads your device clock, so 1:38 AM means 1:38 AM wherever you are, with no time zone to configure. Pressing start schedules a tone for the next 1:38 AM; if that time has already passed today, it is set for tomorrow. The sound is generated in the browser rather than loaded as a file, so it works offline once the page is open. The tab needs to stay open, and on phones the screen should stay awake, since browsers suspend background tabs.
Questions
- How do I set an alarm for 1:38AM?
- Press start above. The alarm sounds at 1:38 AM by your device clock.
- Will the alarm work if I close the tab?
- No. Browsers stop timers in closed tabs, so leave this page open.
- What is 1:38AM in 24-hour time?
- 1:38 AM is 01:38, or 0138 hours in military time.