What the millisecond digit really means
One millisecond is a thousandth of a second (0.001 s). The clock behind this stopwatch, the browser's performance.now(), measures time far more finely than that, so each lap you record is stored at full resolution and exported in milliseconds.
What you see is limited by your screen. A 60 Hz display redraws every 16.7 ms and a 120 Hz display every 8.3 ms, so the last digit jumps in steps instead of ticking through every value. That's normal for any on-screen stopwatch, and it doesn't affect the recorded laps.
What limits real accuracy is the press itself. Human reaction takes roughly 0.15–0.25 s and varies from press to press, so a hand-timed result is honestly good to about a tenth of a second. Use the thousandths to compare your own repeated attempts, or for timing that is triggered the same way each time. The accuracy guide has an interactive breakdown of where the error comes from.
Pick the precision you need
| Display | Format | Good for |
|---|---|---|
| 0.1 s (tenths) | 00:12.3 | Hand-timed races, the precision athletics uses for hand times |
| 0.01 s (hundredths) | 00:12.34 | Training laps, swimming, comparing repeated efforts |
| 0.001 s (milliseconds) | 00:12.345 | Experiments, reaction drills, checking consistency between attempts |
Need several watches at once? Use multiple stopwatches. Want to know your own press delay? Try the reaction time test.
Questions people ask
What is a millisecond stopwatch?
A stopwatch that displays elapsed time to a thousandth of a second (0.001 s), e.g. 00:12.345. This one shows milliseconds by default and stores every lap at full resolution.
What is a 1 millisecond timer?
Usually it means a timer or stopwatch whose display resolves 1 ms steps. The display resolution says nothing about accuracy: a hand-pressed stopwatch is limited by reaction time, roughly 0.15 to 0.25 s per press.
Is it possible to get exactly 0.01 on a stopwatch?
Stopping a stopwatch at 0.01 s is practically impossible by hand. Human reaction is about 0.15 s or more, so the shortest start-stop most people can manage is around a tenth of a second. Try it on our stopwatch game.
What is the most accurate stopwatch?
For official sport, fully automatic electronic timing (a sensor in the start pistol and a photo-finish camera at the finish) is the most accurate, because it removes human presses. For hand timing, the device matters far less than the person; phone, web and dedicated stopwatches all measure time much more precisely than a thumb can press.
Why does the last digit jump instead of counting smoothly?
Screens redraw 60 to 120 times per second, so the display updates every 8 to 17 ms. Recorded laps use the exact press time, not the displayed frame.
Does the millisecond stopwatch keep running in the background?
Yes. It calculates elapsed time from the saved start timestamp, so throttled background tabs, a locked phone or a page reload do not change the result.