Date & time · Stopwatch
Start, pause, lap, repeat.
A clean browser stopwatch with lap splits, pause and resume. Nothing is uploaded or stored.
Stopwatch
Timing is based on performance.now(); the display refreshes about 30 times per second.
00:00.00
Ready
Laps
Each lap records the running total.
Good to know
The result is a guide, not a guarantee.
This calculator runs entirely in your browser. Check the assumptions, keep the inputs realistic, and use the result as a starting point for a decision.
The display depends on the browser's timer scheduling. Closing the tab clears the session.
Does the stopwatch keep running in the background?
It keeps measuring while the tab stays open, although browsers may throttle timers in background tabs. Keep the tab visible for the most accurate display.
How accurate is it?
The timer uses the browser's high-resolution performance clock and updates about every 31 milliseconds. Display precision is hundredths of a second, but screen refresh and browser scheduling affect what you see.
What does a lap record?
Each lap stores the total elapsed time at the moment you press Lap. The smaller split shows the time since the previous lap.
Will it survive a page reload?
No. Refreshing or closing the page clears the stopwatch. Nothing is saved to your device or a server.