Online Stopwatch
Lap History
Click Start or press the space bar to start the stopwatch. TheKronometre shows elapsed time at a 10 millisecond display resolution, records unlimited laps and exports your lap data as a CSV file. Press F for fullscreen and R to reset. No installation, sign-up or browser extension required.
How Does a Stopwatch Work?
A stopwatch is a timing device that measures the interval between two moments. Unlike an ordinary clock it does not show the time of day, but the time elapsed from the moment you start it to the moment you stop it. Every stopwatch has three core parts: a start/stop mechanism, a time display and a reset function.
Stopwatch accuracy is not defined arbitrarily. Stopwatch and Timer Calibrations (NIST Special Publication 960-12), published by the US National Institute of Standards and Technology, defines three calibration methods: direct comparison, the totalize method and the time base method.
The same guide makes a point most users do not expect: in a hand-operated stopwatch the largest single source of total uncertainty is not the device but the person using it. In NIST’s measurements, average human reaction time under the direct comparison method generally stays below ±100 milliseconds, but in the worst cases it can exceed 700 milliseconds. For short intervals, the number you read is largely a measure of your own reflexes rather than of the stopwatch.
We explain exactly what this tool measures — and what it does not guarantee — on our timing accuracy page. For stopwatch types, history and the difference between a stopwatch and a timer, see our What Is a Stopwatch? guide.
What is an Online Stopwatch?
An online stopwatch is a browser-based digital stopwatch that runs on any computer, tablet or smartphone without downloading an app. Online stopwatch tools measure time with the browser’s high-resolution timer and show the result directly in the browser window.
TheKronometre.com offers 6 advantages over phone-based stopwatch apps: zero installation, no storage usage, automatic updates, cross-platform compatibility across Android, iOS, Windows, and macOS, keyboard shortcut support, and full desktop screen utilization. The online stopwatch works on Chrome, Safari, Firefox, and Edge.
Stopwatch History
Louis Moinet, compteur de tierces
Built for astronomical observation, running at 30 Hz and able to read 1/60 of a second (a "tierce"), this instrument resurfaced in 2012 and is now regarded as the earliest known chronograph.
Nicolas Mathieu Rieussec
Rieussec timed the horse races on the Champ de Mars on 1 September 1821 and received a patent for his "seconds chronograph" on 9 March 1822. It marked time by dropping ink onto a rotating dial, reading to 1/5 of a second — the first chronograph built for sports timing.
Adolphe Nicole, the reset mechanism
British patent 10,348: a heart-shaped cam that returns the chronograph hand to its starting point, making consecutive measurements possible.
Adolphe Nicole, the basis of the modern chronograph
British patent 1,461: a column wheel with single-button control. The layout of the modern chronograph descends from this.
Omega, first official Olympic timekeeper
Omega was appointed to time every event at the Los Angeles Olympics. A single watchmaker sent from Biel, with 30 rattrapante chronographs, timed the Games to 1/10 of a second.
Seiko, quartz arrives in sport
Seiko’s Crystal Chronometer QC-951 was the world’s first portable quartz clock, with a daily error of only 0.2 seconds. It served as the master clock for long-distance running at the 1964 Tokyo Olympics.
Seiko Quartz Astron 35SQ
Introduced on 25 December 1969, the first quartz wristwatch sold to the public. Its monthly error was ±5 seconds.
Quartz goes mainstream
Quartz crystals oscillate 32,768 (2¹⁵) times per second. A fifteen-stage divide-by-two circuit reduces this to exactly 1 Hz. The figure is a deliberate balance: high enough to stay above human hearing, low enough to keep the crystal small and power draw low.
Browser-based stopwatches
Timing moved into the browser. Online stopwatches that need no installation and run on any device became commonplace. TheKronometre offers a 10 ms display resolution; we explain what that means on our timing accuracy page.
How to Use the Online Stopwatch
To use this stopwatch tool, follow these 5 steps for a complete timing session.
Basic Usage: Step by Step
Start
Click the START button or press Space on your keyboard to begin timing.
Record Laps
Click the LAP button or press L. Each lap displays individual lap time and cumulative split time.
Pause
Press Space again to Pause. Press Space once more to Resume from the paused position.
Reset
Press R or click Reset to clear the stopwatch to zero.
Export Data
Click CSV Download to export all lap records. Open the file in Excel, Google Sheets, or LibreOffice Calc.
Keyboard Shortcuts
Control the stopwatch without touching the mouse — practical during sports training, exam simulations, and lab experiments.
Use Cases
A digital stopwatch serves 5 primary use cases across sports, education, cooking, productivity, and scientific research.
Sports and Athletics
In training, what matters is not a single finish time but the lap-by-lap distribution. Recording every lap separately and seeing the difference between them is the fastest way to learn pace control. Use the sports stopwatch page to compare training laps and see lap differences.
Official competition is a different matter. World Athletics Technical Rule 19 recognises three official timing methods: hand timing, fully automatic timing from a photo finish system, and transponder timing. On the track, for races up to and including 10,000 m, fully automatic times are recorded to the next longer 0.01 second, while hand times are recorded to the next longer 0.1 second. Photo finish systems must capture at least 1,000 images per second at top-tier competitions. TheKronometre is therefore for training, repeats and personal tracking; official results require certified timing systems.
Study and Exam Preparation
The most neglected exam skill is developing a feel for how long a single question may take. Dividing the total time by the number of questions gives you a reference pace, and training against that reference is what makes it usable under pressure.
These averages are a reference, not a target: finishing easy questions below the average and transferring the time you save to hard ones is the basis of exam strategy. With the lap function you can record the time spent on each question or each section separately, export the results as CSV and track how they change over the weeks. If you prefer working in Pomodoro cycles, switch to the Pomodoro timer page.
Kitchen and Cooking
Cooking precision depends on timing. Pasta reaches al dente in exactly 8 minutes (480 seconds), ±30 seconds. Sugar transitions from caramel to burnt within a 15-second window. French patisserie and Italian cuisine demand second-level accuracy.
The stopwatch's lap recording function tracks multiple cooking stages simultaneously — recording each step without losing the overall elapsed time. Sound alerts notify when time expires, removing the need to watch the screen.
Productivity and Focus Work
The Pomodoro Technique, developed by the Italian author Francesco Cirillo in the 1980s, structures work into focus sessions separated by short breaks. The common arrangement is 25 minutes of work and a 5-minute break.
You can use our Pomodoro timer page, which switches between work and break automatically. Freelancers and remote workers use this arrangement to track completed cycles and total focus time across the day.
Science and Research
Laboratory experiments, reaction-time measurements and observation protocols need timing at millisecond resolution. Pendulum swing measurements, chemical reaction timing and human reaction-time studies all benefit from browser-based measurement with exportable data. For the limits of browser resolution, see our timing accuracy page.
The stopwatch's CSV Export feature allows researchers and university students to transfer timing data directly into analysis programs. Each exported file includes lap number, total time, and split time.
Key Features
TheKronometre.com provides 6 professional-grade features. All are free, with no registration or payment required.
10 ms Display Resolution
Time is measured with the browser’s monotonic high-resolution timer and shown at 10 millisecond resolution. We explain what that means on our timing accuracy page.
Lap Recording & Statistics
Unlimited laps with automatic fastest-lap and slowest-lap highlighting. Each recorded interval shows individual lap time and cumulative split time.
Fullscreen Mode
Distraction-free fullscreen stopwatch for presentations, coaching sessions, and focused timing. Press F to enter, ESC to exit.
CSV Export
Export all lap data with one click. Open exported files in Excel, Google Sheets, or LibreOffice Calc for filtering, charting, and performance analysis.
Keyboard Shortcuts
Space, L, R, and F keys provide full control without mouse interaction. Built for speed during training and exam practice.
All features work across Android, iOS, Windows, and macOS browsers. No installation, subscription, or payment required.
TheKronometre Features
| Feature | TheKronometre |
|---|---|
| Display resolution | ✓ 10 ms |
| Lap recording | ✓ Unlimited |
| Fastest/slowest lap | ✓ Marked automatically |
| Lap difference analysis | ✓ Signed difference column |
| CSV export | ✓ One click |
| Fullscreen | ✓ Built in |
| Keyboard shortcuts | ✓ Full support |
| Offline use | ✓ Yes |
| Installation | ✓ Not required |
| Sign-up / account | ✓ Not required |
| Ads | ✓ None |
| Does data leave your device | ✓ No, it stays in the browser |
Frequently Asked Questions
Everything you need to know about TheKronometre.
How do I use this online stopwatch?
Why choose this tool over other stopwatch tools?
Which devices does the stopwatch work on?
Is lap history saved between sessions?
What keyboard shortcuts are available?
How accurate is the online stopwatch?
performance.now()) and displays it at 10 millisecond resolution. That is a display resolution, not a guarantee of measurement accuracy. All major browsers deliberately coarsen this timer as a mitigation against Spectre-type attacks, and the on-screen number cannot update more often than the display refreshes. See our timing accuracy page for details.All About Stopwatches
Visit our blog to learn how a stopwatch works, which type is best for you, and how to use it more effectively.