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Reaction time test

    On a keyboard, the space bar works like a click.

    The result includes the delay of your screen, your mouse or touchscreen and the browser (often a few tens of milliseconds). Use it to compare yourself with yourself; it is not a medical test. Nothing is sent: everything stays on your device.

    In the same category

    A reaction time test in five tries

    This reaction time test, also called a reflex test, measures your simple reaction time: the delay between a signal appearing and your movement. The area turns red, then green after a wait you cannot predict, and you click as fast as you can. The result is shown in milliseconds (ms), thousandths of a second.

    A simple reaction has three steps: see the signal, decide to act, move your finger.

    How to take the reaction test

    1. Click the large area marked "Click to start", or press the space bar.
    2. The area turns red, with a square and the word "Wait…". The wait lasts 1.5 to 5 seconds and is drawn at random for every try.
    3. As soon as the area turns green, with a circle and the word "Click!", click. Your time appears, for example 231 ms.
    4. A click during red shows "Too soon!": the try does not count and you do it again.
    5. After 5 valid tries you see your "Average", "Best time" and "Slowest time", a bar chart of the 5 times and a rank from Koala to Lightning.

    "Start again" begins a new round and "Copy my score" puts the result on your clipboard. Your personal best, the best 5-try average, stays on your device until you click "Delete my personal best".

    What is a good reaction time?

    For a visual signal, the usual order of magnitude for an adult is around 250 ms. For a sound it is a little shorter. These are rough benchmarks, not standards.

    A sample round: 231, 247, 219, 262 and 236 ms. The total is 1,195 ms, so the average is 1,195 ÷ 5 = 239 ms. The best time is 219 ms, the slowest 262 ms, and the rank shown is "Falcon" (200 to 250 ms).

    What affects your reaction time

    • Tiredness and lack of sleep make it clearly longer.
    • Alcohol slows it down, even in small amounts.
    • Distraction, a phone above all: divided attention reacts later.
    • Age: it is shortest in young adults and lengthens gradually afterwards.
    • Practice gains a few tens of milliseconds on a repeated movement.
    • Caffeine may shorten it slightly when you are tired. It does not replace sleep.

    Reaction time and driving: the sums

    At 50 km/h a car covers 50,000 m in 3,600 s, which is 13.9 m every second. During one second of reaction it travels about 14 m before braking even begins. At 130 km/h the figure is 36.1 m, about 36 m. In miles per hour: 30 mph is 13.4 m per second (44 feet) and 70 mph is 31.3 m per second (about 103 feet).

    The thinking time taught to learner drivers is longer than the time measured here. On the road the hazard is unexpected: you have to notice it, understand it, then move your foot from the accelerator to the brake. In this test you are waiting for a signal you know, with your finger already in place.

    Why results differ from one device to another

    The number on screen also contains hardware delay: the display needs a few milliseconds to show the green, the mouse or touchscreen to pass on the press, the browser to handle it. Together that often adds a few tens of milliseconds, and a phone usually gives longer times than a computer with a mouse.

    A single try says little: a blink is enough to spoil it. That is why the test averages 5 tries.

    Tips for a reliable round

    • Sit somewhere quiet, hand on the mouse or finger just above the screen, and keep to the same device from one round to the next.
    • Do one warm-up round, then compare your averages rather than your single best time.

    Frequently asked questions

    Is this test a medical diagnosis?

    No. It is there to compare yourself with yourself. If you are worried about your reflexes or your attention, talk to a healthcare professional.

    Why does the wait before green change every time?

    So that you react to the signal and not to a rhythm. With a fixed wait you would soon anticipate, and the result would no longer measure anything.

    Is a time under 150 ms possible?

    It is very rare for a visual signal. A time that short usually comes from a click that happened to set off just before green.

    Are my results stored anywhere?

    Only your personal best is kept, in your browser's storage on this device. Nothing is sent over the internet.