Reaction time test

In a study of 1,469 adults aged 18 to 65, the average time to answer a simple light was 230.8 ms^[1]. Most people in that study were within 26.8 ms of the average, either way. Robot tests of everyday devices found that a screen, a browser and a keyboard add 44.1 ms to 115.1 ms more than the study's own equipment, and a touch screen 39.8 ms to 52 ms^[2][3]. Your real time is probably that much quicker than the number you see, so we show where you stand as a range: for example, quicker than about 5 to 9 in 10 adults.

Human Benchmark, a popular website, reports a median of 273 ms (reported by the site)^[4] over many millions of clicks. Its figure counts clicks rather than people, and it mixes every kind of phone, screen and mouse, so we show it as a mark on the ruler and never as a comparison. A good time, then, is one near your own best on the same device: the study tells you where adults stand, your history tells you whether you are getting quicker.

The green screen is drawn at the start of a new picture on your screen, and the clock starts with that picture. Your time is taken from the moment the browser registered your tap, click or key, not from the moment our code got round to reading it. On a 60 Hz screen each picture stays for a sixtieth of a second, so the start of the green is known to within one picture.

A browser cannot see two delays: the time your screen needs to light up the green, and the time your touch screen, mouse or keyboard needs to report the press. Robots that pressed everyday computers and phones found that together they add 44.1 ms to 115.1 ms more than the study's own equipment with a keyboard, and 39.8 ms to 52 ms with a touch screen^[2][3]. No study has timed a mouse this way, so a mouse gets the keyboard's figures, and a pen the touch screen's. Your real time is therefore quicker than the number you see, and that is why we compare you as a range and not as one exact number. On a computer the range is wide, because computers differ a lot: take it as a rough guide.

If you switch to another tab or app during a try, or the screen stalls while the green is showing, that try does not count and you do it again. Your result is saved in this browser and nowhere else: it never goes into a link, and it is never sent to us. You can read about us to see who makes the site.

• A wired mouse or a keyboard reports a press sooner than most wireless mice and touch screens.
• A 144 Hz screen shows the green sooner than a 60 Hz screen, because it draws a new picture more often.
• Other tabs and programs that keep the computer busy can delay the picture that shows the green.

None of these is a reason to worry about one result. They are the reason we always tell you how your result was taken, so that you compare like with like: a phone result with your earlier phone results, a mouse result with your mouse results.

A short night slows most people down more than anything else on this page. Reaction time is also a little slower early in the morning and late at night than in the middle of the day. Practice helps during the first few runs, while you learn the rhythm of the test, and then it levels off.

1. Take the test on the same device each time.
2. Take it at about the same time of day.
3. Compare the middle time of several runs, not your single best try.

Reaction time grows slowly with age. In the study above it rose a little with each year of age^[1]. From one birthday to the next the change is far smaller than the difference between a good night and a bad one, or between two devices. A child is compared with adults here, because the study measured adults.

The wait before the green is chosen at random for every try, so there is no rhythm to learn. A press before the green is a false start, and a press that comes too soon after it to be a reaction is a guess: both are thrown away, and you do that try again. The quickest way to a good result is to watch the screen, keep your finger ready and react to the colour itself.