Reaction Time, Explained

By Udit Agarwal · Updated October 17, 2026

Reaction time is the delay between a signal and your response to it, such as the gap between a panel turning green and your finger pressing the mouse button. For a simple visual task like that, many adults land somewhere around 200 to 250 milliseconds, between a fifth and a quarter of a second. Online tests usually read a little higher than laboratory ones, because the screen and the mouse add their own delay to every click.

What reaction time measures

Every reaction has three stages. Your eyes or ears detect the signal, your brain decides to respond, and a command travels along the nerves to the muscles that make the movement. A reaction time test measures all three together, from the moment the signal appears to the moment the press registers.

Psychologists separate two kinds:

• Simple reaction time has one signal and one response: click when the panel turns green. It is the fastest kind, because there is nothing to choose.
• Choice reaction time has several signals, each with its own response, such as pressing the left key for red and the right key for blue. It is slower, and it grows as the number of options grows. The Hick–Hyman law describes this: the time rises roughly with the logarithm of the number of choices.

The ArrayKit Reaction Time Test measures simple reaction time, to a colour change or, in sound mode, to a beep.

What is a good reaction time?

For many adults, a simple visual reaction time is roughly 200 to 250 ms. Laboratory studies, which use equipment that adds almost no delay of its own, have long reported averages of roughly 180 to 200 ms to a light for young adults. Responses to a sound are usually a few tens of milliseconds faster, with laboratory averages around 140 to 160 ms. On an ordinary computer the same person scores higher, and the ArrayKit test treats about 250 ms as typical.

This is how the ArrayKit test rates the average of a run:

An average under 180 ms is rare on a screen. A very fast single round can be a lucky anticipation rather than a real reaction, and an average of five rounds is far less affected by one lucky click than your best round would be.

Why your screen, mouse and browser add delay

A test that runs on a computer measures your reaction plus the time your equipment takes to show the signal and report the click. The main contributors:

• Display refresh. A 60 Hz screen draws a new frame every 16.7 ms, so a colour change can wait up to that long before it starts to appear. At 144 Hz the gap is 6.9 ms, and at 240 Hz it is 4.2 ms. The screen's own processing adds more, and it varies by model; many TVs offer a game mode that reduces it.
• The mouse. Many standard USB mice report to the computer 125 times a second, once every 8 ms, while gaming mice often report 1,000 times a second, once every millisecond. Wireless and Bluetooth devices, trackpads and touchscreens can add more. The Mouse Tester estimates your mouse's polling rate.
• The computer and browser. The click passes through the operating system and the browser before the page sees it, and a busy computer is slower to draw the next frame.
• Audio output. In sound mode, the beep passes through the sound system before you hear it, and Bluetooth headphones in particular often add a noticeable delay.

Together these commonly add a few tens of milliseconds, and more on a slow setup. That is why a score is only comparable with other scores from the same device, screen and input.

What affects your reaction time

Your equipment aside, these are the factors with the clearest evidence:

• Age. Reaction time is quickest in young adulthood and slows gradually with age. Children are slower than adults too.
• Sleep and fatigue. Lack of sleep slows reactions and causes lapses, rounds where you respond far later than usual. A tired run usually shows up as a higher average and a wider spread.
• Practice. The first few rounds are often slower while you get used to the timing. After a short warm-up the gains tend to be small.
• Caffeine. Studies generally find that caffeine can speed reaction times modestly, mainly in people who are tired.
• Alcohol and sedating medicines. Both slow reactions.
• Distraction. Splitting your attention, such as glancing at a phone, slows responses and makes them less consistent.

How the ArrayKit test measures it

Click the blue panel to start. It turns red and says to wait; after a random pause of 1.5 to 5 seconds it turns green, and you click, tap, or press Space or Enter while the panel has focus, as fast as you can. The random pause stops you from learning a rhythm.

The timer starts in the animation frame in which the panel turns green and stops at the timestamp the browser records for your press, so if the page is slow to handle the click, that delay is not added. The time the screen takes to show the green and the mouse takes to report the click is still included, as it is in any test that runs on a computer.

Clicking while the panel is red shows "Too soon!". That round is thrown away and replayed, the false start is counted and displayed, and it never enters the average. A press stamped before the green appeared counts as too soon as well. After each result, presses are ignored for 0.3 seconds so a double click cannot skip it, and if you switch tabs during a wait, the round is cancelled rather than stretched.

After five valid rounds you get the average (the mean of the five), the median, your best and worst round and the spread, which is the standard deviation of the five times. You also get a rating from the table above and a rough comparison with typical results. Sound mode replaces the colour change with a beep, with a volume control and a sound check. Your last 10 runs and your best average for each signal type are kept in this browser only and can be cleared at any time, and a button copies a one-line result. Timing happens in the tab, and nothing is uploaded.

Reading your results

Suppose your five rounds are 231, 254, 219, 276 and 245 ms. The average is 1,225 ÷ 5 = 245 ms, the median is also 245, the best is 219 and the worst 276, and the spread is about ±22 ms. That run rates as Average.

Now suppose you blinked on the last round and it took 412 ms instead of 245. The average jumps to 278, while the median moves only to 254. The median shows what you can do on a typical round; the average includes your bad moments too. Round-to-round differences of a few tens of milliseconds are normal, so judge yourself by several runs rather than one. The Mean, Median, Mode Calculator and the Standard Deviation Calculator do the same arithmetic for any list of numbers.

How to get a fair score

1. Pick one input, such as a wired mouse, and stick with it. Rest your finger on the button.
2. Keep the test tab in front and your eyes on the middle of the panel.
3. Do one warm-up run, then compare the averages of the next few runs.
4. Compare scores only from the same device, screen and input.
5. React to the green rather than guessing. Early clicks are thrown away anyway, so anticipating only wastes rounds.
6. In sound mode, use wired headphones or speakers.
7. Test when you are rested and not distracted, because both show up in the numbers.

Frequently asked questions

What is a good reaction time? On a screen-based test, about 250 ms is typical for adults, 180 to 229 ms is fast, and under 180 ms is rare. Laboratory equipment reads faster, often around 180 to 200 ms for young adults, because it adds almost no delay of its own.

What is the average human reaction time? For a simple visual signal, many adults react in roughly 200 to 250 ms. Reactions to a sound are usually a few tens of milliseconds quicker. Choice reactions, where you must pick between responses, take longer.

Is 200 ms a good reaction time? Yes. On the ArrayKit test, an average of 200 ms falls in the Fast band, quicker than most people manage on a screen. On laboratory equipment it would be closer to typical for a young adult.

Why is my reaction time slower on a laptop or phone? Trackpads, touchscreens and wireless input devices can add delay before the press reaches the page, and screens differ in how quickly they show the signal. Compare results only on the same device.

Can you improve your reaction time? A little. Scores usually improve over the first few runs as you get used to the test, and being rested and alert helps. A faster screen or mouse lowers the measured time too, although that only trims the equipment's share of the delay.

Is reaction time to sound faster than to sight? Usually, by a few tens of milliseconds in laboratory studies. In a browser, though, speakers and especially Bluetooth headphones can delay the beep, so sound results depend even more on your equipment.

Why does the test use five rounds? Single reactions vary by tens of milliseconds, so one click says little. The average of five valid rounds is steadier, and false starts do not use up a round.

Keep going

• Click Speed Test — count your clicks per second over 1 to 60 seconds.
• Aim Trainer — Gridshot, Flick and Tracking rounds scored for hits, accuracy and time to hit.
• Chimp Test — memorise numbered squares and click them in order.
• Typing Test — measure your words per minute and accuracy.
• Number Memory Test and Visual Memory Test — see how much you can hold in short-term memory.
• Online tests — every test on ArrayKit, from webcam and mic checks to memory games.

Reaction Time Test

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