How to use the reaction time test
- Click the blue box, or focus it and press Space or Enter, to start trial 1.
- The box turns red. Wait: the pause is random, between 1.5 and 4.5 seconds. Click early and it says Too early!; click again to redo that trial.
- When the box turns green, click as fast as you can. Your time in milliseconds appears in the box and in the trial row.
- After five trials the results panel shows Fastest, Slowest, Average and a Rating. Click the box to start a new test.
How it is measured
The timer starts in the frame where the box turns green and stops at the timestamp of your press, taken when the button goes down rather than when it is released. Each trial is rounded to the nearest millisecond, and the average is the sum of the five divided by five. A press less than 100 ms after green is thrown out as a guess, the same cutoff World Athletics uses for false starts (false start rule).
The rating uses your average: under 200 ms is Very fast, 200 to 249 is Fast, 250 to 299 is Typical, and 300 or more is Slower than typical. These are rough guides, not a medical measure. In a study of 1,469 adults aged 18 to 65, the mean simple visual reaction time was 231 ms, or about 213 ms after correcting for equipment delay, and it grew by roughly 0.5 ms per year of age (Woods et al., 2015).
Worked example
Say your five trials are 231, 245, 238, 252 and 229 ms. The panel shows Fastest 229 ms, Slowest 252 ms and Average 239 ms, because (231 + 245 + 238 + 252 + 229) / 5 = 1195 / 5 = 239. That falls in the 200 to 249 band, so the rating is Fast.
Limits and edge cases
- Your score includes screen, input and browser delay, so it is higher than a lab reading. Compare yourself only on the same device.
- If the tab is hidden during a trial, the trial is cancelled and the test waits for your next click.
- Your best average is saved in this browser only, if your browser allows storage.
- For timing longer things use the stopwatch, to test your hands on a keyboard try the typing speed test, and for a two-player game clock see the chess clock.
Frequently asked questions
What is a good reaction time?
About 200 to 250 ms is good for a click on a screen. In a 2015 study of 1,469 adults aged 18 to 65, the average simple visual reaction time was 231 ms. Under 200 ms is very fast, and 300 ms or more is slower than typical.
Why is my reaction time slower on a phone or laptop?
Your result includes the delay of your screen, input device and browser, which adds tens of milliseconds, and touchscreens and trackpads often add more than a wired mouse. To compare yourself over time, use the same device each time.
Why does it say too early or too fast?
Clicking before the box turns green counts as too early. A press within 100 ms after green is also rejected, because people cannot react that quickly, so it was a guess. World Athletics uses the same 0.1 second line for sprint false starts.
Do reaction times change with age or practice?
Yes. The same study found reaction times grow longer by about 0.5 ms per year of age. Sleep, focus and practice also move your score, and early trials are often slower, so judge yourself by the average of all five.
Sources: Woods et al., Frontiers in Human Neuroscience, 2015; False start (athletics). Checked October 2026.