Reaction Time Conversion Table: Milliseconds, Percentile, Ruler Centimetres and Grade

A reaction time score on its own is just a number. This page is a set of lookup tables that turn it into something you can act on: what percentile it puts you in, what grade band it falls into, what ruler catch distance it corresponds to, how it translates between test types, and what it means in metres on a road. Skip to whichever table you need - the reference assumptions behind all of them are spelled out at the bottom.

One rule before you look anything up: convert an average, not a single trial. Reaction time varies by 30-50ms from attempt to attempt for the same person on the same evening, which is easily a whole band on any of these tables. Five trials minimum, best and worst included.

Table 1: milliseconds to percentile and grade

The percentile column answers the question people actually mean when they ask how they did: what share of testers are faster than you. It is calculated from a reference distribution centred on 273ms with a spread (standard deviation) of about 60ms, which is the same distribution our reaction test uses to score results, and is in line with commonly cited figures for adults on simple visual tap tests.

Point percentiles, if you want the exact figure for a round number: 200ms is the 11th percentile, 220ms the 19th, 240ms the 29th, 260ms the 41st, 273ms the 50th, 300ms the 67th, 320ms the 78th, 340ms the 87th and 360ms the 93rd. Lower is better throughout - the percentile is the share of people who are quicker than you, so being in the 11th percentile means only about one tester in nine beats you.

Treat these as approximate. A percentile is only as good as its reference group, and casual online testers are not a random sample of humanity - they skew young, motivated and repeat-tested, which pulls the reference average slightly faster than a truly representative population would be.

Table 2: milliseconds to ruler drop centimetres

If you want to check a screen score against a screen-free method, this table tells you what catch distance the same reaction time should produce on a ruler drop test. It comes from free fall: d = ½gt² with g = 9.81 m/s².

This is why the standard classroom ruler frustrates so many groups: a 30cm ruler cannot record anything slower than 247ms, and the adult average is 273ms. If half your class keeps missing the catch entirely, you need a metre rule, not faster students. The reverse lookup - centimetres to milliseconds in 5cm steps - is on the how to test page.

Table 3: converting between test types

The most common mistake in reaction time comparisons is comparing scores from two different tasks. A choice task inserts a decision stage; a moving-target task adds visual tracking and a spatial aim. Both are slower than a simple task by design. This table gives the rough equivalents for the same person.

The choice column assumes the 80-150ms decision cost that is typically observed with a small number of alternatives; the moving-target column adds a further 30-50ms for tracking and aiming. These are ranges, not formulas - the gap between your simple and choice scores is personal, and it is arguably the most interesting number you can produce. A large gap points at decision speed as your bottleneck; a small gap points at raw signal detection. The mechanics of why are explained in simple vs choice vs serial reaction time.

Table 4: what a millisecond looks like on the road

Reaction time gets quoted in driving discussions constantly, usually with the wrong number attached. This table converts pure reaction delay into distance travelled.

That last row is the important one. A lab reaction time of 250ms is not your braking reaction. On the road you must notice something, decide it matters, decide what to do, and move your foot - a chain that driver-training material commonly puts somewhere between 1 and 2 seconds. Your tap score is one small component of that chain, so use these tables for curiosity and self-tracking, never as evidence about how safely anyone drives.

Worked example: converting one real score

Suppose five trials on a phone come out at 268, 291, 254, 312 and 275ms. The mean is 280ms and the median is 275ms, so the spread is well behaved and either figure is usable - quote the mean, 280ms. Table 1 puts that in the typical band, with roughly 55% of testers faster. Table 2 says the same reaction on a ruler drop should give a catch around 38-39cm, which is past the end of a school ruler, so that person needs a metre rule to reproduce it offline. Table 3 predicts a choice-task score somewhere near 370-430ms for the same person, so if a game reports 390ms there is nothing wrong at all.

Now change one thing: the same person retests on a wired desktop and averages 246ms. Nothing about their nervous system changed in ten minutes - roughly 30ms of that gap is the phone. That is the whole argument for fixing one device and comparing yourself only against yourself.

Assumptions behind these tables

• Reference distribution: mean 273ms, standard deviation 60ms, simple visual tap test on a consumer device.
• Ruler conversion: free fall from rest, g = 9.81 m/s², no air resistance, catch distance measured from the 0cm mark.
• Cross-test ranges: commonly cited decision-stage costs, not measurements from a specific study.
• Scores include device latency. A phone or wireless setup can add 20-70ms that is not biological.

Now that you can read the numbers, get one worth reading: run the three-round test, then check your result against the age chart, or the teenage chart if you are under 18. For a classroom write-up, the experiment template includes a data table built around these conversions.

Frequently asked questions