A countdown timer counts down from the time you set to zero and then alerts you. Set it for the egg on the stove, a 25-minute focus session, a presentation slot or a break between workout sets; it keeps accurate time using your device’s clock and puts the time remaining in the browser tab so you can see it from another page.
How to use the countdown timer
- Set the time by typing hours, minutes and seconds, or tap a preset (1, 5, 10, 15, 30 or 60 minutes).
- Press Start. The display counts down and the tab title shows the time left.
- Pause or resume with the same button, or press Reset to return to your set time.
- When it hits zero the display turns red and the page plays a three-beep alarm.
Countdown timer formula
Time left = end time − current time
Rather than subtracting one second at a time (which drifts when a browser throttles background tabs), the timer computes the finish moment once and then repeatedly asks how far away it is. This keeps the countdown correct even when the page is not in front of you. Minutes above 59 are accepted and normalised, so 90 minutes becomes 1 hour 30 minutes.
Example: a 1 hour 30 minute 15 second timer
- Hours: 1 × 3,600 = 3,600 s.
- Minutes: 30 × 60 = 1,800 s.
- Seconds: 15 s.
- Total: 3,600 + 1,800 + 15 = 5,415 seconds (90.25 minutes), shown as 01:30:15.
Handy timer durations
| Use | Seconds | Timer shows |
|---|---|---|
| Soft-boiled egg | 360 | 00:06:00 |
| Tea steeping | 240 | 00:04:00 |
| Pomodoro focus block | 1500 | 00:25:00 |
| Short break | 300 | 00:05:00 |
| Meeting slot | 1800 | 00:30:00 |
| Oven roast | 5400 | 01:30:00 |
| Dough first rise | 3600 | 01:00:00 |
Cooking times vary by altitude, pan size and equipment, so treat food durations as starting points and check doneness.
Tips for reliable timers
- Allow sound. Browsers may block audio until you interact with the page; pressing Start counts as an interaction.
- Keep the tab open. Closing the page ends the countdown. For long timers, leave the tab pinned.
- Use a phone alarm for anything safety-critical, such as medication or a pot left on the heat.
- Break up large tasks. Short countdowns of 15 to 25 minutes help with focus, followed by a short rest.
Counting up instead? Use the Online Timer and Stopwatch stopwatch. To find the clock time at which a countdown will end, add the duration with the Minutes From Now Calculator or Hours From Now Calculator calculators. For kitchen conversions see the Cooking Conversion Calculator.
Frequently asked questions
How do I set a countdown timer?
Type the hours, minutes and seconds, or tap a preset such as 10 minutes, then press Start. The display counts down to 00:00:00 and the page plays a short beep.
Will the alarm sound if I switch tabs?
The countdown is based on the clock, so it stays accurate in the background, and the tab title shows the time left. Some browsers block sound in background tabs, so keep the volume up and the tab open for important timers.
Can I enter more than 59 minutes?
Yes. 90 minutes is converted to 1 hour 30 minutes automatically.
How long is a Pomodoro?
The classic Pomodoro technique uses 25-minute focus blocks followed by 5-minute breaks, with a longer break after four rounds.
Why does my timer finish a fraction of a second late?
Browsers update the display about every tenth of a second, so the zero may be shown up to a tenth late. The underlying end time is exact.