Set timer for 100 hours
Set a timer for 100 hours in your browser — no app or download needed.
Works on desktop and mobile.
When you set and start a timer, its settings (message, sound) for that duration are saved automatically. Your saved timers appear here. Click one to activate it with one click.
About the 100 hour timer
This page is preset to 100 hours. Add a label or pick a sound, then start the countdown. Click "Start timer" to begin. Use a 100 hours timer for long reminders, events, or extended countdowns. When the countdown reaches zero, the alarm sounds. Use Label and Sound on the widget to change the alarm sound and message. Keep the page open until the timer rings.
How to set a timer for 100 hours
This page is preset to 100 hours. Start the countdown:
- Confirm the duration is 100 hours (or change it if needed).
- Optionally use the Label and Sound rows on the widget to add a message and choose a ringtone.
- Click "Start timer" to begin the countdown. The widget shows the remaining time.
- Keep the browser tab open until the timer reaches zero and the alarm rings. You can pause, resume, or reset the timer.
- Use the toolbar (top right) to zoom in or out or switch to fullscreen.
Use this page as a 100 hour timer for a long-running countdown. Use it for long study sessions, work blocks, meetings, cooking, sleep, or extended countdowns. Alarm settings are saved for future use.
Need a different countdown? Use the main Online Timer. Need to set an alarm? Use the Online Alarm Clock. Want to measure elapsed time? Use the Online Stopwatch. Need to count clicks or events? Try the Online Counter. Want to check the current time? See the Online Clock.
Related time tools
Need to wake up at a specific time? Use the Online Alarm Clock. Track elapsed time with the Online Stopwatch. Count items with the Online Counter. Check the time with the Online Clock.
Frequently asked questions
- Is there a free timer for 100 hours online?
This page is preset to 100 hours. Use Label and Sound on the widget to pick a sound and message, then click "Start timer". Keep the tab open — the alarm sounds when time is up.
- Will the timer work if I close the tab? Why didn't it go off?
The countdown only runs while the page is open. Closing the tab or putting the device to sleep stops the timer. Keep the page visible and check your volume. On mobile, keep the page in the foreground.
- Can I use a different sound or message for my 100 hour timer?
Yes. Use Label and Sound on the widget to add a message and pick a ringtone. Settings save when you start the timer.
- Are my timer settings saved? Can I bookmark a timer?
Sound and message save per duration. Last-used timers appear in "Saved timers". Each timer page has its own URL — bookmark it and settings load with one click. Open different durations in separate tabs for multiple timers.