A stopwatch that is precise and easy to use
This online stopwatch measures elapsed time to the hundredth of a second and records as many laps as you need. It is handy for running and swimming intervals, timing speeches and presentations, cooking, science experiments, board games or measuring how long a task really takes. Press Start to begin, Stop to pause and Start again to continue from where you left off. Reset clears the time and all laps.
Laps and splits
Press Lap while the stopwatch is running to record the current moment. The table shows each lap's own duration (the lap time) and the total time since the start (the split), newest first. Once you have two or more laps, the fastest lap is highlighted in green and the slowest in red, so you can see at a glance how consistent your pace was. Copy laps puts the whole list on your clipboard as tab-separated text that pastes neatly into a spreadsheet.
Keyboard shortcuts
- Space: start or stop.
- L: record a lap.
- R: reset.
Shortcuts are ignored while you are typing in a box or have a button focused, so they never fire by accident. On a phone, the large buttons are easy to tap without looking.
How accurate is it?
Timing uses the browser's high-resolution clock (performance.now), which measures intervals with sub-millisecond precision and is not affected by changes to your computer's clock. The display redraws with the screen, usually 60 times a second. Elapsed time is always worked out from the clock rather than by counting screen updates, so it remains correct even if the tab is in the background and the display pauses. In practice, the main source of error is human reaction time when pressing the button, typically 0.1 to 0.25 seconds, which is why official sports timing uses sensors.
Related tools
To count down from a set time, use the countdown timer; for work and break cycles, the Pomodoro timer; and to check your speed at the keyboard, the typing speed test.