PlanetClocksOnline Stopwatch
A precise stopwatch with lap times, accurate to hundredths of a second. Works on phone and desktop, with keyboard shortcuts.
Keyboard: Space = start/stop, L = lap, R = reset.
How to use the stopwatch
Press Start to begin timing and Stop to pause; press again to resume. While it is running, Lap records a split: the list shows each lap time and the total elapsed time. Reset clears everything. On a keyboard, press Space to start or stop, L for a lap and R to reset.
Accuracy
The stopwatch measures time with the browser's high-resolution monotonic clock (performance.now), which is not affected by changes to your system clock. The display refreshes with every screen frame. Keep in mind that human reaction time when pressing a button is typically 0.15–0.3 seconds, which is far larger than the timing error.
Typical uses
Running and swimming intervals, cooking, presentations and speeches, science experiments, board games, or measuring how long a task takes.
Frequently asked questions
Does the stopwatch work if I switch tabs?
Yes. Time is measured from timestamps, not by counting ticks, so it stays correct even if the browser slows down background tabs.
Is there a time limit?
No practical limit. Hours are shown once the elapsed time passes 60 minutes.
Are my laps saved?
Laps are kept only while the page is open and are never sent anywhere.