What is a Stopwatch?
A stopwatch is a time measurement tool that precisely measures elapsed time. It can measure time down to milliseconds (1/100th of a second) from the moment you press start until you stop. Unlike a timer that counts down from a set time to zero, a stopwatch starts from zero and measures time indefinitely.
- Start: Begin time measurement
- Pause: Temporarily stop measurement
- Resume: Continue from where you paused
- Reset: Return time to zero
- Lap: Record current time while continuing
How to Use the Stopwatch
Getting Started
Click the green 'Start' button to begin. Time is displayed in minutes:seconds.milliseconds format.
Recording Laps
Press 'Lap' while running to record split times. Useful for comparing different segments.
Pause & Resume
Use 'Pause' to stop and 'Resume' to continue measuring from where you left off.
Managing Records
Lap records are auto-saved. Export to Excel or delete individual entries.
Stopwatch Use Cases
Study & Focus
Track study time with Pomodoro technique (25 min work + 5 min break) or measure total daily study hours.
Sports & Fitness
Record workout times and lap splits for running, swimming, cycling. Perfect for interval training.
Game Speedruns
Measure game completion times and compare segment records. Challenge your personal best.
Cooking Timing
Perfect for precise cooking times - boiling pasta, grilling steaks, and more.
Work Productivity
Measure time spent on tasks to analyze and improve work efficiency.
Test & Competition Prep
Practice solving problems within time limits or rehearse presentations.
Frequently Asked Questions
What's the difference between a stopwatch and a timer?
A stopwatch starts from zero and measures elapsed time indefinitely, while a timer counts down from a set time to zero. Use a stopwatch for 'how long did it take' and a timer for 'how much time is left'.
Will my records be saved if I close the browser?
Lap records are automatically saved in your browser's local storage. You can access previous records when returning with the same browser. However, clearing browser data will also delete records.
Can I use other apps while the stopwatch is running?
As long as the browser tab remains open, the stopwatch keeps running even while you use other apps. Just be careful not to close the tab entirely, as that will stop the measurement. On mobile, simply keep the browser in the background.
What's the maximum measurement time?
There's no time limit - measure indefinitely. Times over 1 hour are displayed in hours:minutes:seconds.milliseconds format.
Can I save lap records?
Yes, click 'Export Excel' to download all lap records as a CSV file. Open it in Excel or Google Sheets.
Digital vs Mechanical Stopwatches
Digital stopwatches rely on quartz crystal oscillators vibrating at 32,768 Hz, achieving inherent accuracy of about ±0.01 seconds per hour. Browser-based stopwatches use JavaScript's performance.now() API, which provides sub-millisecond resolution tied to your device's system clock.
In practice, the biggest source of error is human reaction time, averaging 200-250 milliseconds. This is why professional sports use automated electronic timing systems — photo-finish cameras and touchpads — that eliminate human delay entirely and measure to 1/1000th of a second.
Sports Timing Standards
Track & Field (World Athletics): Times are recorded to 1/100th of a second using Fully Automatic Timing (FAT) systems with photo-finish cameras. A false start is detected by sensors measuring reaction times under 0.100 seconds.
Swimming (World Aquatics): Touchpads at the pool wall record times to 1/100th of a second. The pads require only 1.5-2.5 kg of pressure to register, ensuring fair timing regardless of how hard a swimmer finishes.
Formula 1 (FIA): Lap times are measured to 1/1000th of a second using transponders embedded in each car. Sector times help teams analyze performance across different segments of the circuit.
Marathon: Chip timing with RFID transponders measures net time (from crossing the start line) rather than gun time, accurate to about 1/10th of a second.
Privacy Notice
Stopwatch records are processed only in your browser and are not transmitted to any server. Lap records and settings are stored only in the browser's local storage, so there is no risk of your personal data being leaked.