IQ Test
Most free IQ tests hand you a number pulled from a lookup table. This one estimates your ability with a 2-parameter logistic IRT model, selects each item to match your running ability estimate, and reports a full-scale score with an honest confidence interval.
How to use IQ Test
- Choose a track — balanced, or weighted toward maths, language, visual or memory.
- Work through each timed subtest; difficulty adapts to your answers.
- Finish the battery without pausing for the most accurate estimate.
- Read your full-scale score, confidence interval and per-domain profile.
About IQ Test
The difference between a real cognitive assessment and a free online quiz is not the questions — it is the scoring. A quiz counts correct answers and maps the total onto a scale someone invented. A psychometric instrument models the difficulty and discrimination of each individual item and estimates the ability level that best explains your particular pattern of responses. Getting a very hard item right tells you far more than getting an easy one right, and the maths should reflect that.
This test uses a 2-parameter logistic item response model to do exactly that. Every item carries calibrated difficulty and discrimination parameters, your ability estimate is updated as you work, and the next item is selected to sit near your current estimate — which is where it yields the most information. Subtest scores are combined by information weighting rather than a flat average, so the domains measured most precisely count for most.
It also reports its own uncertainty. Any single sitting of any test produces a range, not a point, so the result is given as a full-scale score with a 95% confidence interval alongside a percentile and a per-domain profile. That is less flattering than a bare three-digit number, and considerably more honest. It remains a self-administered test taken in uncontrolled conditions, not a clinical assessment.
Frequently asked questions
Is this IQ test accurate?
It uses the same statistical machinery as professional instruments — 2PL item response theory, adaptive item selection and information-weighted compositing — and reports a confidence interval rather than a false-precision single number. It is not a clinical diagnosis, but it is far more principled than a fixed 20-question quiz.
How long does it take?
Between 20 and 35 minutes depending on the track you choose. Each subtest is individually timed.
Is it free and private?
Completely free with no sign-up, and every item, response and score stays in your own browser’s storage.
Can I retake it?
Yes. Items are procedurally generated and previously-seen items are tracked, so retakes stay meaningful rather than rewarding memorisation.
What does the confidence interval on my score mean?
It is the range within which your true ability most plausibly sits, given how much information the items you saw actually provided. A result of 118 with an interval of 111–125 is saying that 118 is the best single guess and that anything in that band is consistent with your answers.
Why does the test get harder when I answer correctly?
Because an item near your own ability level is the one that tells the model most. A question you would certainly get right, or certainly get wrong, contributes almost nothing, so difficulty is steered towards the point of maximum information and the whole battery reaches a given precision in far fewer items.
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- Number Memory Test — How many digits can you hold?
- Sequence Memory Test — Repeat the growing pattern
- Visual Memory Test — Remember the lit squares