IQ scores are not counts of anything. They are rankings dressed up as numbers.
Modern tests are built so the average score in the population is exactly 100. The spread around that average is fixed too. On the Wechsler tests, one standard deviation equals 15 points.
So an IQ of 120 is 20 points above average. In standard deviations, that is 1.33 above the mean.
The number itself is arbitrary. The position it describes is not.
This is why the same raw performance can produce different IQ numbers on different tests. The scale is a convention, chosen by the test publisher.
It also explains something that confuses people. Your IQ score is always relative to other people your age, not to some fixed standard of ability.
The history of intelligence testing shows how deliberately that design choice was made.
Where an IQ of 120 Sits on the Curve
IQ scores follow a normal distribution, the familiar bell curve. Most people cluster near the middle. Numbers thin out fast in both directions.
An IQ of 120 falls at about the 91st percentile. Put plainly, you would score higher than roughly 91 out of 100 randomly chosen people.
That translates to about 1 person in 11. In a workplace of 100, roughly nine colleagues would score at or above your level.
It is worth pausing on that. An IQ of 120 is genuinely uncommon, but it is not rare. Most people will meet several dozen such people in a lifetime without ever noticing.
