Stopwatch
Free online stopwatch with lap times — big centisecond display, Start/Pause/Resume, and a lap table that highlights your best and slowest laps.
About the Stopwatch
This online stopwatch measures elapsed time to the centisecond (1/100 of a second) on a huge, glanceable display. Start, pause, resume and reset with single clicks — no download or signup, it runs entirely in your browser on desktop and mobile.
The Lap button records split times while the clock keeps running: each row in the lap table shows the individual lap time and the cumulative total, with your best lap highlighted and your slowest flagged. That makes it ideal for interval training, swimming and running splits, speedcubing, science experiments and timing anything repetitive.
Under the hood it uses your browser's high-resolution monotonic clock (performance.now) rather than counting timer ticks, so the reading stays accurate even if the page briefly lags — the display refreshes every 10 milliseconds but the time itself is always computed from the real clock.
How to Use the Stopwatch
- 1Click Start to begin timing.
- 2Click Lap to record a split without stopping the clock.
- 3Use Pause and Resume as needed — laps and total time are preserved.
- 4Click Reset to clear the time and the lap table.
Frequently Asked Questions
How accurate is an online stopwatch?
Very accurate for everyday use. This stopwatch derives elapsed time from your browser's high-resolution monotonic clock instead of adding up ticks, so even if the display briefly stutters the underlying measurement doesn't drift. Expect accuracy within a few milliseconds — human reaction time (~200 ms) is a far bigger factor.
What's the difference between lap time and total time?
Total is the time from the very start; lap time is the duration since the previous lap press. If you press Lap at 1:00 and again at 2:30, the second lap time is 1:30 with a total of 2:30. The table shows both for every lap, newest first, so you can track splits and overall time together.
What do the best and slowest highlights mean?
Once you have at least two laps, the fastest individual lap is highlighted and labeled Best, and the slowest is marked. This mirrors how sports lap timers work, making it easy to spot your strongest interval and your fade — useful for pacing runs, swim sets and HIIT rounds.
What does the .00 part of the display mean?
Those are centiseconds — hundredths of a second. The display format is minutes:seconds.centiseconds, so 01:23.45 means 1 minute, 23 seconds and 450 milliseconds. Centisecond precision is the standard for sports timing and matches physical stopwatches.
Does the stopwatch keep running if I switch tabs?
Yes. Because the elapsed time is calculated from the real clock, switching tabs or windows doesn't lose time — when you come back the display catches up instantly to the true elapsed value. Closing the page entirely does reset it, though, as nothing is stored.