Free Online Stopwatch
Measure elapsed time with precision. Use the stopwatch for sports, cooking, studying, or any activity that needs accurate timing.
Lap times
How to Use the Online Stopwatch
Click Start to begin timing. The stopwatch counts upward with millisecond precision. Use the Lap button to record split times without stopping the clock — useful for tracking intervals in workouts, races, or experiments. Hit Stop to pause, then Resume to continue or Reset to start fresh.
Stopwatch vs. Timer
The stopwatch measures elapsed time by counting up — you use it when you don't know in advance how long something will take. The online timer counts down from a set duration and alerts you when it reaches zero. To be reminded at a specific clock time, use the alarm clock.
Need to see your current time or timezone? Check the current time page or compare times across cities with the world clock.
How precise is a browser stopwatch?
The stopwatch reads the browser's high-resolution clock, which reports elapsed time in fractions of a millisecond, and displays hundredths of a second. The display itself refreshes about sixty times per second, so what you see may lag the true value by up to 16 milliseconds, but the value recorded when you press Lap or Stop is taken from the clock at that instant, not from the display. In practice the limiting factor is your reaction time on the button, which for most adults is between 200 and 300 milliseconds. You can measure yours with the reaction time test.
For long recordings the stopwatch stays accurate for the same reason the timer does: elapsed time is computed as the difference between the current clock and the moment you pressed Start, so a background tab that was throttled catches up instantly when you return to it.
Laps and splits explained
Pressing Lap records the elapsed time without stopping the clock. Each entry shows two numbers: the split (total time since Start) and the lap (time since the previous lap). Swimmers and runners use lap times to see whether they are fading; a coach timing a 400 m interval session cares about each 100 m lap, while the athlete's official result is the final split. If you need statistics across many laps, fastest, slowest, average, or want to copy them out for a spreadsheet, the dedicated lap timer adds those features on top of the same engine.
Keyboard shortcuts and screen modes
The space bar starts and stops the stopwatch, and L records a lap, so you can keep your eyes on what you are timing rather than on the cursor. On a phone the whole display area is a tap target. Full-screen mode turns the page into a large, high-contrast readout suitable for a gym wall, a science lab bench or a cooking demonstration where several people need to read the time from a distance.
When to use a stopwatch and when not to
- Measuring how long something takes, with an unknown end: a stopwatch. Time your commute, a presentation rehearsal, a sourdough proof, a child's reading fluency passage.
- Counting down a known duration: the timer. You want an alert at the end, and a stopwatch never alerts.
- Repeating work and rest blocks: the interval timer or Tabata timer; they switch phases and sound cues automatically.
- Timing turns for two people: the chess clock, which runs two clocks that alternate.
Popular Stopwatch Uses
Sports Timing
Time running laps, swimming splits, or cycling intervals. Record each lap to track your progress.
Speed Cubing
Measure your Rubik's cube solve time with millisecond precision. Track your personal best.
Science Experiments
Accurately measure reaction times, chemical processes, or any experiment requiring precise time tracking.
Frequently Asked Questions
How accurate is the online stopwatch?
The stopwatch uses your browser's high-resolution timer, providing millisecond-level accuracy.
Can I record lap times?
Yes. Click the Lap button while the stopwatch is running to record split times.
What is the difference between the stopwatch and the timer?
The stopwatch counts up to measure elapsed time. The timer counts down from a set duration and alerts you when it reaches zero. Use the stopwatch when you want to measure how long something takes.
Can I set an alarm to go off at a specific time?
The stopwatch doesn't support alarms. For that, use the online alarm clock to set an alert for a specific time, or the timer for a countdown.