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Online stopwatch with millisecond precision. Start, stop, reset, and record lap times. Uses performance.now() for accurate timing. No signup required.
A stopwatch measures elapsed time from a starting point, with millisecond precision. Used for timing events, workouts, cooking, and scientific experiments.
00:00.000
Formula
Elapsed Time = Current Time − Start Time + Accumulated Pause TimeCurrent Time = the current high-resolution timestamp from performance.now()
Start Time = the timestamp when the stopwatch was last started or resumed
Accumulated Pause Time = total elapsed time from previous start-pause cycles
Worked Example
Timing a 400m sprint with lap splits
Did you know? The first stopwatch was invented by Nicolas Mathieu Rieussec in 1821 for King Louis XVIII to time horse races. Modern digital stopwatches achieve accuracy to 1/1000th of a second.
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