12 Hour Timer (12h)
Free online 12 hour (12h) countdown timer with alarm
Space start/pause · R reset · +− adjust
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Keep this countdown beside other tasks in Multiple Timers →Related Timers
Embed this timer
Paste this into any page — a class blog, a lesson plan, a meeting agenda — and visitors get a working 12 hour timer with no script tag, no account and no tracking. Please keep the credit link.
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.
Common Uses
- Sleep timer
- Overnight countdown
- Slow roast or braise
- Work shift timer
- Fasting window check
How to Use the 12 Hour Timer
- Click Start (or press Space) to begin your 12 hour countdown
- Press Space again to pause and resume, or R to reset the timer
- Use the +/- buttons to adjust by 5 minutes while running
- Toggle Repeat to loop the countdown automatically, and watch the finish time under the display
- Use the Fullscreen control below the timer for a large full-screen countdown (Esc to exit)
- Pick a background sound — rain, ocean, fireplace or brown noise — that fades out at zero
- Choose or mute the alarm sound from the sound settings in the header
- Add
?autostart=1to the link to start the countdown on load - Enable notifications for alerts when your 12 hour timer finishes, even in a background tab
Frequently Asked Questions
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.