Chronometer
A high-precision stopwatch with lap recording, split times, and lap statistics — all running locally in your browser.
The chronometer runs entirely in your browser. No data is sent, tracked, or stored on any server. Timer state resets on page refresh.
A precision stopwatch is a surprisingly versatile tool — athletes use it to track lap times,
developers measure code performance, speakers time presentations, and cooks monitor recipes.
Our free Chronometer delivers centisecond-level
accuracy with a clean, distraction-free interface. Start and pause the timer with a single
large button, record laps with individual lap times and cumulative splits, and get instant
statistics including your best lap, worst lap, and average lap time. The high-contrast
monospace display is easy to read from across the room, and everything runs in your
browser's JavaScript engine with setInterval at 10ms resolution.
How to Use the Chronometer
- Start the timer — Press the green Start button. The display immediately begins counting up in HH:MM:SS.00 format.
- Record a lap — While the timer is running, click the Lap button. Each lap records the individual lap time and the cumulative split time at that moment.
- Review statistics — The lap list shows the best lap highlighted in green, the worst in red, and displays the average lap time in the header.
- Pause or reset — Press Pause to freeze the display without losing laps, or Reset to clear everything and start over.
Key Features
- Centisecond Precision
Displays up to HH:MM:SS.00 with 10ms update intervals for highly accurate timing.
- Lap Recording
Record unlimited laps with individual lap times and cumulative split times — best and worst laps highlighted automatically.
- Lap Statistics
Instantly see your best lap time, worst lap time, and average lap duration across all recorded laps.
- Pause & Resume
Pause the timer to freeze the display while keeping all lap data intact. Resume when ready to continue.
- Large Readable Display
Monospace font at 7-8xl sizing — easily readable from across a room or track.
- 100% Client-Side
No network requests, no data collection. The timer runs fully offline once the page has loaded.
Frequently Asked Questions
How accurate is the chronometer?
Date.now() and a 10ms setInterval for display updates. While this is suitable for most use cases (sports timing, presentations,
cooking), it is not suitable for sub-millisecond scientific measurement. Browser timers are
subject to throttling when the tab is in the background.What happens if I switch tabs?
Date.now() rather than incrementing a counter. Even if the browser throttles the update interval in a
background tab, the displayed time jumps to the correct value when you return.