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CALCPARK

Reaction Time Test

Click or press Space when the box turns green. Five trials give your average, best and median reaction time in ms against the typical 250 ms, with false-start detection.

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How to use it

  1. Click the box or press Space. It turns red: wait.
  2. After a random 2–5 seconds the box turns green. Click, tap or press Space as fast as you can.
  3. Read the trial time, then press again for the next trial. A press on red is a false start; the trial is repeated.
  4. After five valid trials you get the average, median, fastest and slowest time plus a rating; the best five-trial average is kept in your browser.
  5. “Copy results” puts all five times and the summary on the clipboard; “Try again” or R starts a new set.

Example

Five trials of 231, 262, 198, 287 and 244 ms give an average of 244 ms(rated “average”: 225–274 ms), a median of 244 ms, a best of 198 ms, a slowest of 287 ms and a spread of ±33 ms. One press while the box was still red would be listed as a false start and would not change any of these numbers.

What the test measures and how it is scored

This is a simplereaction-time task: one stimulus (the colour change) and one fixed response (the press). Recognition and choice reaction tasks, where you must decide which of several signals appeared or which key to press, take 50–150 ms longer. Each trial is timed with performance.now(), a sub-millisecond monotonic clock, from the moment the green state is rendered to the pointerdown or keydownevent. The delay before the green signal is drawn uniformly from 2,000–5,000 ms using the browser’s cryptographic random source, so the signal cannot be predicted from a rhythm.

average = (t1 + t2 + t3 + t4 + t5) / 5    median = 3rd fastest of the five    spread = sample standard deviation

The rating bands are centred on the 250 ms figure: below 175 ms exceptional, 175–224 faster than average, 225–274 average, 275–324 slightly slower, 325–374 slower, 375 ms and above much slower than average. Kosinski’s review of the literature puts the mean simple visual reaction time of college-age adults at roughly 190–250 ms depending on the apparatus; the Nintendo Wii Balance Board study of 354 adults aged 20–99 found a significant non-linear increase with age for both hands and feet, with men slightly faster than women. Web-based tests like this one sit at the slower end of those ranges because of display and input latency, which is why the typical value is marked at 250 ms rather than 200.

Sources: Kosinski, R. J. – A Literature Review on Reaction Time (Clemson University), Blomkvist et al. (2017) – Reference data on reaction time and aging using the Nintendo Wii Balance Board, PLOS ONE 12(12), Woods et al. (2015) – Factors influencing the latency of simple reaction time, Frontiers in Human Neuroscience 9:131, MDN – performance.now().

How to get a fair measurement

  • Use a mouse or keyboard rather than a touch screen when you can: touch input adds the most latency.
  • Keep your finger resting on the key or button and look at the centre of the box, not at the timer.
  • Run the five trials in one sitting and compare only results from the same device and browser.
  • A 60 Hz display updates every 16.7 ms, so the green frame can appear up to 16 ms after the clock starts; a 144 Hz screen halves that.

Questions

What is a good reaction time?
On a browser test, 200–250 ms is good for an adult and anything under 200 ms is excellent; most people land between 220 and 300 ms. Competitive gamers and athletes in sprint starts often record 150–200 ms, and sprint starts under 100 ms are ruled false starts for the same reason this test rejects them.
Why was my fast trial counted as a false start?
A measured time under 100 ms cannot be a response to the green signal – visual processing alone takes longer – so it means you pressed on a guess that happened to land just after the change. The trial is repeated so your average reflects real reactions.
Why do I score slower here than on the same test elsewhere?
The measurement includes your screen, input device and browser. A laptop touchpad, a wireless mouse in power-saving mode or a touch screen can add 20–40 ms compared with a wired mouse on a fast monitor. Compare results against your own earlier runs on the same setup; the best average kept in this browser is meant for exactly that.