How the start lights work
Press Space or tap the lights to begin. Five pairs of red lights come on, one pair every second. Once all five are lit, they stay on for a random time between 0.2 and 3 seconds, then all go out together.
Because the wait is random, you cannot count it. You have to watch and react, just like a race start.
What is a good reaction time?
Most people react to a light in about a quarter of a second. Here is a rough guide for this test:
- Under 200 ms is very fast.
- 200 to 270 ms is typical. The average adult lands around 250 ms.
- 270 to 400 ms is a little slow, often from being tired or distracted.
- Over 400 ms usually means your attention drifted. Try again.
Jump starts
If you press while any light is still on, it counts as a jump start and no time is recorded. Racing drivers face the same rule.
Times under about 100 ms are faster than people can really react to a light, so they are almost always a lucky guess.
Tips for a faster time
- Rest your finger on the key or the screen before the lights come on.
- Look at the middle of the lights, not at one pair.
- Use the same device each time, so your results compare fairly.
- Take a few tries. Your average of the last ten says more than one lucky run.
Questions and answers
How is my reaction time measured?
The test starts counting on the screen frame where the lights go out and stops at the moment your tap or key press arrives. The timer is accurate to about a millisecond, but your screen and input device add a small delay, usually between 10 and 50 ms.
Why is my time slower on my phone?
Touch screens and wireless keyboards take a little longer to report a press than a wired keyboard or mouse. Compare results on the same device for a fair picture.
What is the average human reaction time?
For a simple reaction to a light, most adults take about 250 milliseconds. Practice, rest and focus can bring that down, and being tired pushes it up.
Can I use the keyboard?
Yes. Press Space or Enter to start, and press it again when the lights go out. You can also click or tap anywhere on the lights.
Are my results saved?
Your last ten times and your best time are kept in this browser, so they are still there when you come back. Nothing is sent anywhere. Use Clear results to start over.