3 Hour Timer

The page opens with 3 in the Hours box, which is 180 minutes or 10,800 seconds. You can start straight away.

1. Skip Quick start. Its longest choice is 1 hour, so it shows Custom time while the boxes below hold your three hours.
2. Check Hours (3), Minutes (0) and Seconds (0). Adjust them for a paper that runs 2 hours 45 minutes, for example, and the digits change at once.
3. Write a Label (optional) such as Mock exam or Roast. It appears above the clock and again in the Time is up message.
4. Leave Play a sound when time is up ticked unless you need silence, then press Start. The clock counts down from 03:00:00.
5. Press Pause and Resume for breaks, Reset to go back to the full time, and Full screen to fill the display with a large clock.

Space starts and pauses, and R resets while stopped, as long as the cursor is outside a text box.

A three hour block rewards a plan. In numbers, it is 180 minutes, 10,800 seconds, or one eighth of a day. The progress bar fills by about 0.56 percent each minute, so it is a third full after one hour.

Take a mock exam worth 100 marks over three hours. If you keep the last 15 minutes for checking, 165 minutes are left, or 1.65 minutes per mark. Spread over three sections, the plan looks like this:

The times add up to 180 minutes, because section B is rounded up from 49.5 and section C is rounded down from 82.5. Write the three checkpoints on a sheet before you begin and glance at the clock only at those moments.

The same arithmetic suits a deep work half day. One approach is two blocks of 80 minutes with a 20 minute break, which totals exactly 180. Another is to run this page for the whole session and nest shorter countdowns, such as the 90 minute timer, inside it. Use the time calculator when you want to add the blocks and breaks and check the total.

For cooking, a slow roast or braise can take about three hours at a low oven temperature. The timer reminds you to check, but the recipe and a food thermometer decide when the meat is done, since cuts, ovens and pans all differ.

Short timers fail quietly and cost little. A three hour one is different, because it depends on a browser tab staying alive for a long time. Several things can interrupt it:

• Screen lock and sleep. Many phones and laptops sleep after a few minutes. The page asks for the screen to stay awake on browsers that support it, but this is a request, not a promise.
• Battery. A screen that stays lit for three hours uses a noticeable amount of power, so plug in a laptop or tablet.
• Closed or reloaded tabs. Closing the tab ends the count, and the timer is not saved. Reloading also starts again from the full time.
• Silent alarms. The sound plays only if the tab is open and the device is not muted. There is no repeat and no notification pop-up.

For anything with a hard deadline, such as picking someone up from a flight or ending an invigilated test, set a second alarm on your phone clock. A long flight leg is a good example: this page cannot help once the device is in a bag or switched off, so use it for planning before boarding and let the aircraft schedule decide the rest.

The count is measured against your device clock, so a hidden tab stays accurate even if the sound arrives a little late. If you know the time you want to stop, not the length, the online alarm clock is simpler than doing the sum. For a shorter block, try the 2 hour timer.