Reaction Time Test

How to use the reaction time test

1. Press the large box, or press Space or Enter while it has focus, to begin. The box turns red and asks you to wait.
2. Keep your hand ready but do not click. After a random wait between 1.5 and 5 seconds the box turns green and says Click now!
3. Click, tap or press a key as soon as you see green. Your time in milliseconds appears at once, with a plain rating.
4. Click again for another attempt. The cards below update with your latest time, a last 5 average, the overall average, median, best, slowest and spread.
5. Use Copy results or Download CSV to keep your numbers, or Reset to start a fresh session.

How the timing works

When the wait ends, the page asks the browser to draw the green box. On the next animation frame the page reads the high resolution clock, performance.now(), and stores that reading as the start. When you click, the tool takes the timestamp the browser attached to your input event and subtracts the start. Using the event timestamp instead of the moment the page code runs removes a few milliseconds of scheduling delay.

The wait is random so you cannot learn the rhythm. The delay is drawn from a secure random source with no modulo bias, uniform over whole milliseconds from 1,500 to 5,000. A click before green counts as a false start. It is shown in the counters but never added to your times, because a guess is not a reaction.

Why your number is higher than your nervous system

The result is the whole chain from screen to input, not just your brain. A display refreshing 60 times a second can show a change up to about 16.7 milliseconds after the page requested it, because 1,000 divided by 60 is about 16.7. Your screen may add processing delay, and your mouse, trackpad, touchscreen or keyboard adds its own delay before the browser sees the event. Wireless and Bluetooth devices usually add more than wired ones.

That means two people on different devices cannot fairly compare scores, and the same person will often score differently on a phone, a laptop and a gaming monitor. For a fair comparison, use the same device and input every time. This is a fun and useful benchmark for yourself, not a clinical test.

Reading the statistics

The last 5 average shows how you are doing right now, while the average covers the whole session. The median is the middle value, so one slow distracted click barely moves it. The spread is the sample standard deviation: the smaller it is, the more consistent you are. For example, times of 200, 250, 300 and 350 milliseconds have an average of 275, a median of 275 and a spread of about 64.5 milliseconds.

The rating words are this tool's own simple labels for one click: under 200 ms is very quick, 200 to 249 quick, 250 to 299 typical, 300 to 399 a little slow, and 400 or more slow. They describe the number on your device, not your health, age or ability. Tiredness, distraction and device lag can all change a result.

Privacy

Nothing you do here leaves your browser. The page saves only your single best time in this browser so it can show it next visit. Reset clears the session but keeps that best time.

Assumptions and limits

• Times include display, input device and browser delay, so they are not a pure measure of nervous system speed.
• A false start is shown in the counter and is not counted as an attempt.
• Only your best time is saved, in this browser. Clearing site data removes it.
• The rating bands are simple labels created for this tool and are not a medical or scientific standard.
• The session keeps your most recent 200 attempts and the table shows the latest 20.

Formulas reviewed October 10, 2026. See the calculation methodology for how SumPanda rounds, tests and sources its formulas.

Frequently asked questions