Online Stopwatch

The stopwatch counts up from zero and keeps a list of laps beside the clock. Nothing is stored on a server.

1. Choose how the time appears in Show: Hundredths of a second, which reads like 01:32.45, or Whole seconds, which reads 01:32.
2. Press Start. While the clock runs the button reads Pause, and after you pause it reads Resume, continuing from where it stopped.
3. Press Lap at each checkpoint. The clock keeps going, and a new row appears in the laps list with the lap number, the lap time and the total so far. The newest lap is at the top.
4. Pause the clock at the finish and read the table. Once there are three or more laps, the fastest lap turns green and the slowest red.
5. Press Copy laps above the list to copy the table as tab-separated text, then paste it into a spreadsheet. Press Reset to clear the time and every lap.

Space starts and pauses, L records a lap and R resets. They work whenever the cursor is not in a text box, and R only resets while the clock is stopped. After the first hour the display adds hours, as in 01:05:30.20.

The Lap time column is the time since the previous lap press, and Total is the time since you started. Each total equals the previous total plus the new lap time. Here is a runner timing four laps of a 400 metre track:

Check the arithmetic: 92.45 + 89.80 + 91.10 + 94.65 = 368.00 seconds, which is 6:08.00. The average lap is 368 / 4 = 92.00 seconds. Copy the lap times and paste the four values into the average calculator to confirm that, and to see the spread. The same laps give a pace of 400 m in 92 s, or 3:50 per kilometre, which the running pace calculator can convert into other distances. The gap between the fastest lap (89.80) and the slowest (94.65) is 4.85 seconds, and the slowest lap came last, which hints at fading near the finish.

The same method works away from the track. To rehearse a talk, press Lap at each slide change and see which section runs long. Rows copied with Copy laps follow the Show setting, so choose Whole seconds first if you do not want hundredths in the spreadsheet. Spreadsheets sometimes read values such as 01:32.45 as clock times, so check the cell format after pasting. To convert a minutes and seconds figure into plain seconds, the time converter does it.

Elapsed time comes from the system clock, and the display refreshes about 30 times a second. A tab that the browser slows down while it is hidden therefore still shows the right time when you come back. The hundredths digit shows the resolution of the display, not the accuracy of the result. Your own reaction time, often 0.1 to 0.3 seconds on each press, matters far more than the clock, and browsers may also coarsen timer precision for privacy. A 10.00 second interval measured by hand can easily be out by a few tenths.

• Not official timing. Use it for training, cooking, games, speaking practice and classroom activities, not for races that need certified results.
• Nothing is saved. Closing the tab or reloading the page loses the time and the laps. Press Copy laps before you leave.
• Counting up only. To stop at a set time, switch to the countdown timer.
• Laps have no names. Each row has only a number, so note what each checkpoint meant on paper or in a spreadsheet column.

For repeating timed blocks of work, the Pomodoro timer is a better fit than lap presses.