Guides
Short, sourced explainers on what IQ scores are, how they are built, and how much weight any single number deserves. Every claim links to the research behind it.
IQ score ranges and percentiles
A full table from 55 to 145 with percentiles and rarity, what the classification labels mean, why rarity accelerates at the tails, and the measurement error most tables leave out.
Read → 7 minWhat is an average IQ?
Why the average is exactly 100 by construction rather than by measurement, how renorming and the Flynn effect work, how scores change with age, and why national IQ tables are unreliable.
Read → 8 minWhat IQ actually predicts
School results, job performance, income and lifespan - with the correlations stated plainly, including the 2022 revision that cut the job-performance estimate from 0.51 to 0.31.
Read → 9 minCan you improve your IQ?
Brain training barely transfers; education reliably adds one to five points a year. The honest evidence on raising a score versus raising the ability underneath it.
Read → 9 minHow IQ changes with age
Fluid reasoning declines while vocabulary keeps rising into the sixties - and age norming is why your score can stay flat through all of it.
Read → 8 minFluid vs crystallised intelligence
The distinction Cattell drew in 1963, how each ability is measured, why they move in opposite directions across a lifetime, and whether fluid reasoning can be trained.
Read → 8 minWorking memory and intelligence
One of the strongest correlates of reasoning ability, why matrix items lean on it so heavily, and why training it still fails to raise IQ.
Read → 8 minIQ vs EQ
Emotional intelligence is real but smaller than the popular claim. Ability EI, trait EI, the personality overlap, and where "matters more than IQ" came from.
Read → 8 minAre IQ tests biased?
Bias has three distinct technical meanings and none of them is "a score gap". What the evidence settles, what it cannot, and where this test is weakest.
Read → 9 minAre online IQ tests accurate?
Reliability, validity and norming - the three properties that separate a defensible online test from a number generator. Includes an eight-point checklist and this site marked against it.
Read → 9 minHow IQ tests are built and normed
Blueprint, item piloting, item statistics, standardisation sample, reliability and validity - and which stage cheap tests quietly skip.
Read → 9 minThe main types of IQ test
Clinical batteries, non-verbal matrices, group tests and online tests compared on what they sample, who may administer them, and what their scores support.
Read → 8 minHow Raven's Progressive Matrices work
The design that has dominated non-verbal testing since 1938, what makes one item harder than another, and why this site generates its own rather than using the originals.
Read → 8 minMensa and high-IQ societies
The 98th percentile criterion, why it converts to 130, 132 or 148 depending on the scale, and why no unsupervised online score can ever qualify you.
Read → 8 minIQ test practice questions, with worked answers
Six worked examples covering every question type on this site - matrices, boolean figure logic, number and letter series, spatial rotation and verbal analogies - with the reasoning spelled out.
Read → 10 minHow these are written
Every factual claim on these pages is either sourced to a named paper or textbook, or is a statement about how this site itself works. Where the research is contested - and in this field a good deal of it is - the guides say so rather than picking the tidier answer.
Where a claim concerns this test specifically, it links to the methodology page, which describes the actual shipped implementation rather than an idealised version of it.
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