BodyCalWhat this reaction time test measures
This is a simple visual reaction time test: the box starts red, turns green after a random delay, and your job is to click the instant you see the change. The number you get is the time, in milliseconds (ms), between green appearing and your click registering. Because the delay is random, you can't anticipate it — you have to genuinely react, which is exactly what makes the result meaningful.
Take several attempts. A single try can be thrown off by a lucky guess or a momentary lapse, so your best and average over a handful of goes are the numbers worth paying attention to.
What counts as a fast reaction time?
For visual reactions, here's roughly how the milliseconds stack up:
- Under 150 ms — exceptional, near the physiological limit of human vision.
- 150–200 ms — fast; typical of trained gamers, athletes, and younger adults.
- 200–250 ms — above average to average for most adults.
- 250–300 ms — average; perfectly normal.
- Over 300 ms — slower than average, often due to fatigue, distraction, or screen lag rather than your actual reflexes.
Why you can't hit zero
Even a perfect human can't react instantly. Light has to hit your retina, the signal travels to your visual cortex, your brain recognises the change, and a command travels back down to your finger — a chain that takes well over 100 ms on its own. On top of that, your monitor takes several milliseconds to physically paint the green pixels, and your mouse and the browser add a little more. That's why this test notes that your true reflex speed is slightly faster than the figure on screen.
What affects your score
Reaction time isn't fixed — it swings with your state and your setup. The biggest factors are sleep and alertness, caffeine, time of day, age, practice, and distraction. Hardware matters too: a high-refresh-rate monitor and a low-latency mouse can shave a meaningful chunk off your number compared to an older laptop screen. For the fairest result, test when you're rested, remove distractions, warm up with a few goes, and compare like with like.
How to improve your reaction time
The evidence points to a few reliable levers: get consistent sleep, exercise regularly (aerobic fitness is linked to faster reactions), stay hydrated, and practise — reaction time improves measurably with repetition before plateauing. Anticipation and focus help in the moment, but remember the hard floor: no human trains their way much below 150 ms for vision. If you enjoy benchmarking yourself, try it daily and watch your average drift down as you dial in your routine — then explore our other quick tools like the BMI calculator and body fat calculator to round out your health picture.