Online Stopwatch
A clean stopwatch with lap times, accurate to a tenth of a second — for workouts, laps, experiments and games.
About this tool
A stopwatch measures the opposite direction from a timer: not how long is left, but how long something took. This one counts up with tenths of a second, and the Lap button records split times without stopping the clock — for intervals, swim and run laps, science experiments, speed-cubing, or timing how long a task really takes.
It runs entirely in your browser and keeps counting in a background tab. Lap times stack newest-first so your latest split is always on top.
How to use it
- Press Start to begin counting.
- Press Lap at each split — each entry shows the total elapsed time and that lap's own duration, and the clock keeps running.
- Press Stop to finish, and Reset to clear everything.
Frequently asked questions
How accurate is the stopwatch?
It is timed from your device's clock and displays tenths of a second. For casual and training use it is effectively exact; certified competition timing uses dedicated equipment.
Does it keep running in a background tab?
Yes — the elapsed time is calculated from the clock, not from screen updates, so switching tabs does not lose time.
Can I record more than one lap?
As many as you like — each Lap press adds a numbered entry to the list.