What Is IQ? Meaning, Origin, and the Basics of the Intelligence Quotient

IQ stands for Intelligence Quotient. It's a word we hear constantly on TV and online, yet surprisingly few people can explain precisely what it means. This article covers the meaning, origin, and mechanics of IQ from the ground up.

The meaning and origin of IQ

IQ is short for Intelligence Quotient. Originally it really was a quotient: mental age divided by chronological age, times 100. Modern tests calculate it differently, using the 'deviation IQ' — your relative position within your own age group. For the full story, see the history of IQ tests.

The mean is 100, the standard deviation 15

Modern IQ is calibrated so the average of each age group is exactly 100 with a standard deviation of 15. An IQ of 115 puts you in roughly the top 16%, and an IQ of 130 in about the top 2% — the number directly encodes your position in the population. See the basics of IQ's average and distribution for details.

'High IQ = smart' is half true

IQ correlates well with the core of intellectual ability (the g factor) — reasoning and pattern recognition — but it does not measure creativity, interpersonal skill, or persistence. It is a strong partial predictor of academic and job performance, yet not a number that determines a person's worth or potential. That is the standard view in psychology.

How to measure your own IQ

Formal assessment means an individually administered test such as the WAIS, given by a psychologist. If you just want a quick estimate first, an online test is the easy way in. BrainRank's free IQ test takes about 10 minutes for 20 questions and returns your estimated IQ, deviation score, and top percentile — no sign-up required.