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

> IQ (intelligence quotient) is a relative score that shows where your cognitive ability sits within your age group. Modern tests are standardized to a mean of 100 and a standard deviation of 15, and mainly measure reasoning and pattern recognition.

- URL: https://brainrank.jp/en/blog/what-is-iq
- Published: 2026-07-19
- Updated: 2026-09-04
- Publisher: BrainRank Editorial Team (https://brainrank.jp)

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](https://brainrank.jp/en/blog/history-of-iq-test).

## 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](https://brainrank.jp/en/iq/130) in about the top 2% — the number directly encodes your position in the population. See [the basics of IQ's average and distribution](https://brainrank.jp/en/blog/iq-average) for details.

## 'High IQ = smart' is half true

IQ correlates well with the core of intellectual ability ([the g factor](https://brainrank.jp/en/blog/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](https://brainrank.jp/en/blog/iq-tests-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](https://brainrank.jp/en/start) takes about 10 minutes for 20 questions and returns your estimated IQ, deviation score, and top percentile — no sign-up required.

## Frequently asked questions

### What is IQ?

IQ stands for intelligence quotient: a relative measure of where a person's cognitive ability sits within their age group.

### What is the average IQ?

Major modern intelligence tests are standardized so that the average for an age group is 100 with a standard deviation of 15.

### What does a high IQ tell you?

It indicates that reasoning, pattern recognition, and problem-solving tend to be strong relative to the same age group. It does not measure creativity, social skills, or a person's worth.

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Statistics and percentages are calculated from a normal distribution model with a mean of 100 and a standard deviation of 15. The tests on this site provide estimates for entertainment and self-understanding; they are not medical or clinical assessments, nor official intelligence tests.
When citing, credit "BrainRank (brainrank.jp)" and link the article URL.