Online Stopwatch
A simple stopwatch with lap times, running in your browser.
00:00.00
Press start to begin timing, lap to record a split and stop to freeze the time. It works on any device with a browser, and there is nothing to install.
Elapsed time is measured against the clock, not by counting screen updates, so it stays accurate even if the tab is in the background or the display refreshes slowly.
How online stopwatch works
The stopwatch stores the moment you pressed start and computes the elapsed time from the browser's high-resolution clock each time it redraws. Pausing stores the time so far, and resuming continues from there.
Each lap shows the split time (since the previous lap) and the total. The fastest and slowest laps are marked. Browsers may reduce clock precision for privacy, so treat the last digit as approximate.
Worked example: timing three laps
Lap 1 at 1:12.40, lap 2 at 2:21.10, lap 3 at 3:35.80.
Splits: 1:12.40, 1:08.70 and 1:14.70, so lap 2 was the fastest.
When to use this tool
- Timing runs, swims and other training laps.
- Timing a presentation or a study block.
- Timing cooking steps and experiments.
Common mistakes to avoid
- Relying on a phone stopwatch page for events where a fraction of a second decides a result. Use certified timing equipment there.
- Letting the device sleep. Keep the screen on for long sessions, since some devices throttle background pages.
Frequently asked questions
- Does the stopwatch keep running in the background?
- Yes. It measures elapsed time from the start moment, so switching tabs does not cause it to lose time.
- How accurate is it?
- It displays hundredths of a second. Browser timers and human reaction time limit real accuracy to a few hundredths at best.
- How do I record lap times?
- Press Lap while the stopwatch is running. Each lap shows its split and the total time.
Learn more
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Results are for information only and are not financial, legal or medical advice. The calculation logic is covered by automated tests, and examples on this page are worked out and re-checked before publishing. Spotted a mistake? Tell us.