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3 Hour Timer
Your 3:00:00 countdown is ready: press Start (or Space) and the alarm sounds after three hours. Useful for long exams, slow roasts, parking limits and study marathons.
3:00:00
Ready
Presets
Shortcuts: Space start / pause · R reset · F fullscreen. Add ?m=90 to the address for a custom length. Keep this tab open; the countdown stays accurate in the background.
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How to use the 3 Hour Timer
- Press Start or hit the Space bar. The 3:00:00 countdown begins immediately.
- Want a reminder midway? Tick Soft chime at the halfway mark to hear a gentle chime at 1:30:00 left.
- Fine-tune the length with the ± buttons or pick another preset.
- Choose an alarm sound and volume, then press Play test sound to check you can hear it.
- When time is up, press Stop alarm or Space. Press R to reset to 3:00:00.
How long is 3 hour?
| Measure | 3 Hour equals |
|---|---|
| Minutes | 180 min |
| Seconds | 10,800 s |
| Milliseconds | 10,800,000 ms |
| Hours | 3 h |
| Share of a day | 12.5% (1/8 of a day) |
| Walking at 5 km/h (3.1 mph) | about 15 km (9 mi) |
| Speaking at 130 words per minute | about 23,400 words |
| Reading at 230 words per minute | about 41,400 words |
What you can do in 3 hour
| Activity | Why 3 hour works |
|---|---|
| Long exam | Many final exams and professional tests last about 3 hours |
| Slow roast or smoke | Pork shoulder pieces, briskets and stews often need 3 hours or more |
| Parking limit | A reminder before a 3 hour parking zone runs out |
| Study marathon | Use the halfway chime at 1:30:00 for a break |
| Marathon goal | Running a marathon in under 3 hours is a famous amateur milestone |
| Charging and curing | Battery charging, glue curing and dough proofing |
How the countdown keeps exact time
When you press Start, the timer records the end moment as start time + 10,800,000 ms on the browser's monotonic clock (performance.now()). Every screen update subtracts the current time from that end moment instead of counting ticks, so a throttled background tab or a busy computer cannot make it fall behind. Pausing stores the time left, and Resume sets a new end moment that far in the future.
Frequently asked questions
How do I set a timer for 3 hours?
The timer opens at 3:00:00. Press Start or the Space bar and it rings when it reaches zero.
How many minutes and seconds are in 3 hours?
3 hours is 180 minutes, 10,800 seconds or 10,800,000 milliseconds.
Will the timer stay accurate for three hours?
Yes, as long as the tab stays open and the device does not sleep. It always works out the time left from the clock, so it cannot drift.
How do I change the length?
Use −5 min / +5 min, the presets from 1 to 5 hours, or ?m= in the address (for example ?m=150). The maximum is 8 hours.
When does the halfway chime play?
If switched on, it plays once when 1:30:00 is left.
Can I get a notification?
Yes. Tick "Notify me when time's up" and allow notifications so you are alerted even if the tab is in the background.
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