Other durations
1 minute2 minutes3 minutes5 minutes10 minutes15 minutes20 minutes25 minutes30 minutes40 minutes45 minutes1 hour1 hour 30 minutes2 hours3 hours4 hours5 hours6 hours7 hours8 hours9 hours10 hours12 hours
About a 5 hours alarm
5 hours is about 3.3 sleep cycles of 90 minutes. If you want to wake at the end of a cycle, the alarms below at 4 hours 30 minutes and 6 hours are the closest cycle boundaries.
The alarm is created as a one-time alarm at the exact clock time, so you can see it in the list above, rename it, or switch the sound. Keep this tab open with the volume up; on desktop it rings from a background tab, on a phone keep the page in the foreground and the screen stays on automatically.
Prefer a countdown?
If you want to watch the time tick down rather than set a clock time, use the 300 minute timer instead. Both ring with the same sounds.