Use the stopwatch for a live session
A stopwatch measures time after you start it. It is useful for a practice run, a study session, a short experiment, or timing a task you repeat. Unlike a countdown, it does not need a target date. The display shows hours, minutes, seconds, and hundredths of a second for the current browser session.
Start timing
Press Start when the activity begins. The clock advances from zero, or from the paused value if you are resuming.
Record a lap if needed
Press Lap while the clock is running to record the total elapsed time at that point. Timing continues.
Pause or reset
Pause stops accumulation until you press Start again. Reset clears both the elapsed time and every lap entry.
What a lap entry represents
Each lap is a cumulative reading from the start of the timed session, excluding periods when the stopwatch was paused. It is not automatically the duration since the previous lap. To find a segment duration, subtract the previous cumulative reading from the current one. The first lap already describes the first segment because the starting value was zero.
| Lap | Recorded total | Segment duration |
|---|---|---|
| 1 | 00:00:30.00 | 30 seconds |
| 2 | 00:01:05.00 | 35 seconds |
| 3 | 00:01:45.00 | 40 seconds |
Pausing changes what you measure
Suppose you work for ten minutes, pause for a five-minute break, and resume for another ten minutes. The stopwatch records twenty minutes of active timed work. Twenty-five minutes have passed on the wall clock. Decide whether breaks belong in your measurement before starting, then apply the same rule to each session you compare.
Displayed precision and practical accuracy
Hundredths make it easier to distinguish short readings, but the display is not a guarantee of hundredth-of-a-second measurement accuracy. Screen refresh, browser scheduling, and your reaction time all affect what you observe and when you press a button. For practice or everyday estimates that may be sufficient; for formal performance measurement, use equipment and a procedure suited to that task.
While the page remains active, elapsed time is derived from a browser timing clock rather than by counting display refreshes. A background tab may update less frequently, and device sleep can affect browser timing behaviour. Keep the page visible and the device awake when measuring a session you intend to compare closely with others.
Keeping a useful record
Record the task, timing rule, and lap readings before you reset or refresh. This stopwatch does not save or export a session. For a task with known start and finish clock times, use the time duration calculator. For a future target, use countdown. See measuring elapsed time for more examples of choosing and interpreting a measurement.