What a 12 hour timer is good for
Each suggestion opens in a space with a matching scene and alarm.
How to use the 12 hour timer
- Press StartThe 12 hour countdown begins at once. The Space bar starts and pauses it too; R resets it.
- Adjust as you goUse − and + to change it by 5 minutes, or click the digits and type any time, like 12:30, 1h30 or until 5:30pm.
- Hear the alarmA loud bell and beep rings at zero until you press Stop, with a vibration on phones. Pick a chime, a shorter ring or a silent glow under More.
- Make it yoursPick a scene and sound, press Fullscreen for a room-sized Clear view (Esc to exit), turn on notifications for a background tab, or add
?autostart=1to the link to start on load.
Shortcuts
SpaceStart / pauseRReset+Add time (− removes it)FFullscreen
Single-key shortcuts can be switched off under More.
12 hour timer at a glance
| Accuracy | Counts to an absolute finish time, so it stays exact in a background tab and after the device sleeps. How the timing is tested |
|---|---|
| Alarm | Loud bell & beep that rings until you press Stop, with the whole screen flooding sunrise-warm. Chime, bell, beep, a shorter ring or a silent glow under More. |
| Display | Large digits that never jitter, a progress horizon, and a fullscreen Clear view (or Daylight, for bright rooms) readable across a room. |
| Sound | Optional rain, ocean, fireplace, café, night, brown or white noise and a focus pad — made in your browser, faded out at zero. |
| Memory | A running or paused countdown survives a reload or a browser restart, saved on this device only. |
| Price | Free. No ads, no signup, nothing to install — and it works offline once visited. |
Other ways to time 12 hours
The same countdown as a picture, a soundscape, a projector view or a video.
About the 12 hour timer
A 12 hour countdown for overnight and full-shift timing. It recovers exactly after device sleep, shows the finish time and date, plays optional rain or brown noise, and alarms at zero.
TimerHub calculates remaining time from an absolute finish timestamp, so missed browser callbacks do not create drift. Read the timing accuracy methodology and reproducible tests.
12h timertimer 12 hoursset a timer for 12 hours12 hour countdown timer
12 hour timer FAQ
How long is 12 hours in minutes?
12 hours is exactly 720 minutes or 43,200 seconds. Our free 12-hour countdown timer tracks every second and sounds an alarm when done.
What is a 12 hour timer used for?
A 12 hour timer is commonly used for sleep timer, overnight countdown, slow roast or braise. Set the countdown and focus on your task with confidence.
Does the timer work in the background?
Yes, our timer continues running even if you switch to another tab or minimize your browser. Enable push notifications to get alerted when your countdown finishes.
Will the alarm sound after 12 hours?
Yes, an alarm sound plays automatically when the 12-hour countdown reaches zero. You can also enable push notifications for an extra alert, even if you’re in another tab.
Can I make the timer fullscreen?
Yes, use the Fullscreen control below the timer for a distraction-free full-screen countdown — useful for long study sessions, offices, and shared screens. Press Esc to exit fullscreen.