How the Main IQ Test works

What the test measures

The Main IQ Test samples four broad abilities from the Cattell-Horn-Carroll (CHC) model, the framework most modern cognitive batteries are built on. Logical Reasoning and Pattern Recognition tap fluid reasoning (Gf) — solving novel problems without leaning on learned content — with Pattern Recognition weighted towards induction specifically. Spatial Intelligence taps visual processing (Gv). Verbal Ability taps crystallised knowledge (Gc): what you have learned and can retrieve. Memory taps working memory (Gwm), holding and manipulating information over seconds. Twenty-five items across those five domains produce both a composite score and a domain profile.

How the adaptive engine works

The test is adaptive: each question is chosen from how you have answered so far. Answer correctly and the next item is harder; miss one and the next is easier. This keeps you near the edge of your ability, where each answer carries the most information about you, and it means two people rarely see the same twenty-five questions. The benefit is precision per minute. A well-targeted short test separates ability levels about as sharply as a much longer fixed one, because the items you would obviously pass, or obviously fail, are never shown.

The banked-time system

Rather than one countdown for the whole test, you are credited 45 seconds as each question appears, and unused time carries forward. Spend twenty seconds on an easy item and the remaining twenty-five stay in your bank for a harder one later. This does two useful things. It removes the ambient panic of a single shrinking clock, which measures anxiety as much as reasoning. And it keeps the test genuinely timed, so nobody can sit on a hard item and look the answer up, which also keeps completion times comparable between takers.

How scoring works

Every item carries a difficulty weight, so a correct answer on a hard question contributes more than a correct answer on an easy one. That is why two people with the same number of items right can finish with different scores. Your weighted performance is then mapped onto the conventional deviation-IQ scale, which places the mean at 100 and the standard deviation at 15 — the scale on which 85 and 115 sit one standard deviation either side of the middle. Domain scores are computed the same way from the items belonging to each domain.

Where percentiles come from

Your percentile is derived from our own accumulated test-taker data, together with the standard assumption that scores follow a normal distribution with a standard deviation of 15. It is not drawn from a professionally stratified, nationally representative standardisation sample. We do not have one, and we will not claim one. Our takers are people who chose to take an IQ test online, which is not the same as the general population. Read your percentile as an accurate position among people like our test-takers, and a reasonable but imperfect estimate of your standing more broadly.

Confidence intervals and measurement error

Every psychometric score carries measurement error. Two sittings by the same person will differ, and a twenty-five-item online test carries more of that error than a two-hour supervised battery does. So we report a 95% confidence interval beside your score and ask you to read the interval rather than the point. The interval widens towards the extremes, where a short test has fewer items to discriminate with. If your score sits near a band boundary, the honest reading is that you are near that boundary — not decisively on one side of it.

What this test is not

This is an online self-assessment. It is not a clinical instrument, it produces no diagnosis, and it should not be used for any decision — educational placement, hiring, medical or legal — that calls for a formal assessment. Supervised, individually administered batteries such as the WAIS and the Stanford-Binet remain the gold standard: professionally normed, delivered by a trained examiner who can see when something is off, and able to reach abilities a text-based online test cannot. We are not affiliated with, or endorsed by, the publishers of those instruments.

Retesting

You may retake the test, and your score will move. Familiarity with the item formats reliably adds a few points on an early retest before levelling off, and that gain reflects recognition rather than new ability. If you want a second reading worth having, leave at least a few weeks, take it rested, at a similar time of day, on the same kind of device, and somewhere quiet. The average of two honest sittings is a better estimate of you than either one on its own.

Fairness and language

The test is offered in 20 languages, and every item is written rather than drawn. Text-based items translate reliably and work with screen readers, but they carry a cost worth stating plainly: verbal items depend on the vocabulary and phrasing of the language you take them in, so someone working in a second language can score below what their reasoning warrants. Our translations are human-reviewed rather than machine-dumped, and the fluid-reasoning items are written to lean on structure instead of idiom. The effect is reduced, not removed.

The Fast & Accurate IQ Test (Quick, Normal, Full)

Next to the Standard test we offer the Fast & Accurate IQ Test, a culture-fair test in three lengths: Quick (15 items), Normal (30) and Full (45). Its items are pictures only — matrices, figural analogies, series, picture completion, odd-one-out, number patterns and short visual working-memory items — and every run is generated from a fresh random seed, so no two runs share an item and the answer key never leaves the server.

Items are weighted by difficulty (1 to 5 points). The weighted raw score is converted to a deviation IQ (mean 100, SD 15) with provisional norms derived from the typical difficulty of these item types; they are replaced by norms from our own completed runs once a form has 500 of them. The confidence interval follows the form's assumed reliability (0.80, 0.88 and 0.92): about ±9, ±5 and ±4 IQ points. Because ±9 is too wide to justify a single number, the Quick form reports a range; the Full form, with nine items per domain, also reports a score per domain. Runs that are far too fast or below chance level are flagged instead of scored.

Our promise

Every number in your report is computed from your own answers: the score, the domain profile, the percentile, the confidence interval. Nothing is decorative, nothing is generated to flatter you, and no figure is invented because it would look impressive. We do not claim norms we do not have, validity we have not established, or clinical standing we do not hold. Where our data is thin or our method has limits, this page says so in plain words. If you believe a number here is wrong, tell us and we will show you how it was produced.