About the Online Stopwatch
This online stopwatch times anything to the hundredth of a second, right in your browser. Press Start, tap Lap to record splits without stopping the clock, and Stop or Reset when you are done. It keeps accurate time even if you switch tabs, because it measures elapsed time from the system clock rather than counting ticks, and you can control it from the keyboard (Space to start/stop, L for lap, R to reset).
Use it for running, swimming and cycling intervals, timing presentations and speeches, experiments and lab work, cooking, puzzles, games and workouts. Every lap shows its own time and the cumulative split, and your fastest and slowest laps are highlighted so you can spot changes in pace.
Already have lap times from a watch or a race result? Paste them into the lap analyser below to get the total time, average lap, fastest and slowest lap and the spread between them.
How to use the online stopwatch
- 1Press Start (or the Space bar) to begin timing.
- 2Press Lap (or L) to record a lap without stopping the clock.
- 3Press Stop to pause and Start again to resume.
- 4Press Reset (or R) to clear the time and laps.
- 5Paste lap times into the analyser to get totals and averages.
Formula and method
The stopwatch records the system clock when you press Start and shows now − start, so the display stays accurate even if the browser throttles a background tab. Each Lap press stores the elapsed time: the lap time is the difference from the previous lap press, and the split is the running total since Start.
The lap analyser converts each entry to seconds (minutes × 60 + seconds, with hours if given), then sums them for the total, divides by the number of laps for the average, and compares the fastest and slowest laps. A negative split means the second half was faster than the first.
- Lap time
- Time between two consecutive Lap presses
- Split
- Cumulative time from Start to that lap
Worked examples
Four 400 m laps
The four laps add up to 62.4 + 58.9 + 60.7 + 59.6 = 241.6 seconds, or 4:01.60. The average lap is 60.4 seconds and the gap between the slowest and fastest lap is 3.5 seconds.
Presentation run-through in sections
The four sections take 135 + 280 + 185.5 + 110 = 710.5 seconds, which is 11 minutes 50.5 seconds. The shortest section was the 1:50 closing.
Frequently asked questions
How accurate is this online stopwatch?+
It reads the browser’s high-resolution clock and displays hundredths of a second. Accuracy is limited mainly by human reaction time when pressing the button, typically 0.1–0.25 seconds, not by the stopwatch itself.
Does the stopwatch keep running if I switch tabs?+
Yes. It calculates elapsed time from the moment you pressed Start, so switching tabs, locking the screen briefly or a slow device will not make it lose time.
What is the difference between a lap and a split?+
A lap time is the time for one segment, from one Lap press to the next. A split is the cumulative time from the start to that point. The table shows both for every lap.
Are there keyboard shortcuts?+
Yes: Space starts and stops, L records a lap and R resets. Shortcuts work when the stopwatch panel is focused, so click it once first.
What is a negative split?+
A negative split means you completed the second half faster than the first. Runners and swimmers aim for it because it usually means pace was well judged. The analyser tells you whether your laps show one.