A simple, accurate stopwatch
Time a run, a presentation, a cooking step, a science experiment, a quiz round or a plank challenge without installing an app. This stopwatch measures time to one hundredth of a second, records lap and split times, and works on phones, tablets and computers. Big digits make it easy to read from a distance.
How to use the stopwatch
- Click Start (or press the space bar) to begin timing.
- Click Lap (or press L) each time a lap or stage is finished. The time keeps running.
- Click Stop to pause and Resume to continue, then Reset (or press R) to clear everything.
- Click Copy laps to paste your results into a spreadsheet or message.
Lap time vs split time
- Lap time is the time for one lap only, from the previous lap press to this one. It shows whether you are speeding up or slowing down.
- Total (split) time is the time since the start, at the moment you pressed Lap.
When you have three or more laps, the fastest lap is shown in green and the slowest in red, which makes it easy to analyse running intervals or swimming lengths.
How accurate is it?
The stopwatch uses the browser's high-resolution clock (performance.now()), which is accurate to a fraction of a millisecond and is not affected by changes to your computer's clock. The display refreshes with every screen frame. The real limit on accuracy is human reaction time, about 0.15 to 0.25 seconds, so for official sports timing, electronic timing systems are used.
Ideas for using a stopwatch
- Track interval training: 400 m repeats, cycling sprints or skipping rounds.
- Practise a speech or interview answer to fit a time limit.
- Measure how long tasks really take to improve your planning.
- Time experiments, such as a pendulum's swing, in physics practicals.
Frequently asked questions
Does it keep running if I switch tabs?
Yes. The time is calculated from the start moment, so it stays correct even if the display pauses in a background tab.
Can I count down instead?
Use the Countdown Timer, which sounds an alarm at zero.
Are my lap times saved?
No. Copy them before closing or reloading the page.