Guides
IQ guides
Five long explainers that between them answer almost every question people arrive with. Start at the top if the subject is new to you.
These are the reference pages the rest of the site links back to. Each one is written to be read on its own, states its sources in the text, and says plainly where the evidence stops and the argument begins.
Everything in this section
What is IQ?
The definition, the scale, what the tests sample, the four things they do not measure, and what a score predicts.
Read more →The IQ scale explained
Where 100 and 15 come from, what a standard deviation does, why the same person gets different numbers on different scales.
Read more →How an IQ score is calculated
Raw score, age norms, scaled and index scores, and the confidence interval that should always travel with the number.
Read more →Types of IQ tests
Individual, group, non-verbal, achievement and online. What each family is for and which one you actually need.
Read more →Are online IQ tests accurate?
The four structural limits that better questions cannot fix, and five signals that separate a serious test from a lead magnet.
Read more →How this site scores its test
What we map raw scores against, why we report a band, and what we would need in order to claim more.
Read more →Start with your own result
Ten questions, no sign-up, and a band rather than an invented number.