The short answer is that you take a test. But which test, who gives it and how you read the result change how much the number actually means. A two-hour assessment with a psychologist and a ten-minute quiz on your phone don't tell you the same kind of thing.
It helps to clear up one common misunderstanding first. IQ isn't a fixed value stored somewhere, like a blood test result. It's a ranking: your performance on a test compared with that of a large group of people your age. So "I want to know my IQ" really means "I want to be compared against a well-built yardstick." The better the comparison group, the more you can trust the score.
The most reliable route: a clinical test with a psychologist
If you want an official IQ score, this is the only real option. For adults, the most widely used instrument is the Wechsler Adult Intelligence Scale (WAIS); for children, there's the child version from the same family (WISC). Only psychologists trained to administer them can give these tests, and for good reason.
The assessment is one-on-one and usually takes an hour to an hour and a half. There isn't a single question type. You'll be asked to explain what words mean, rebuild a pattern with blocks, repeat strings of numbers backwards and match symbols against the clock. Each subtest looks at a different skill: verbal comprehension, visual reasoning, working memory, processing speed.
That's why a clinical report won't give you just one number. Next to the full-scale score you'll see separate scores for each area and a confidence interval, something like "full scale 108, 95% confidence range 103–113." The range isn't a weakness. No test measures a person perfectly with a single figure, and a good report says so.
Often the part that matters most is the sub-scores. Someone with strong verbal scores but noticeably slow processing speed may land on an "average" total, yet that gap might be exactly what explains their struggles at school or work. When psychologists assess learning difficulties or attention problems, they look at this profile far more than the total.
Who actually needs a clinical test?
Getting one out of curiosity is your call, but most people don't need it. The cases where it really helps are fairly specific:
- A child shows signs of a learning difficulty, a developmental delay or unusual giftedness. The school counsellor is a sensible first stop and can point you to the right service.
- An adult notices a new change in attention, memory or thinking speed. Here an IQ test is usually one part of a broader neuropsychological assessment.
- An institution, application or official process asks for a documented result.
High-IQ societies like Mensa are another example. To join, you generally either sit their own supervised test or submit a clinical result they accept. A screenshot from a website won't do.
What online tests can and can't tell you
Most tests on the internet are missing one key thing: norming. That means giving the questions to a large, representative sample of people and scaling the scores to match. Without it, the "118" on your screen comes from the test's own formula, not from a real ranking.
That doesn't make online tests useless. A well-made one uses the same kinds of tasks real intelligence tests do, such as matrix puzzles, number sequences and working-memory tasks, and can give you a rough sense of your strengths and weak spots. Our IQ test is built that way: 28 questions across seven skill areas, about 15–20 minutes. It still isn't an official score, and we say so plainly on the methodology page.
A few signs help you judge whether an online test is worth taking seriously:
- Are the questions real reasoning problems with right answers, or "which colour describes you" filler?
- Does it explain how the score is calculated and where its limits are?
- Does it ask for payment or a phone number before showing your result? If so, measuring you probably isn't the point.
- Does everyone seem to score over 120? Try it with a few friends. In a real distribution, most people cluster around the average.
Can you estimate it without a test?
Not really. School grades, your job or how much you read can be loosely related to intelligence, but working out someone's IQ from them doesn't give consistent results. Grades also reflect study habits, motivation and the school itself.
Our own guesses aren't much better. Research shows only a weak link between how people rate their own IQ and what they actually score. Some overrate themselves, some sell themselves short. "I'd say I'm around 130" usually tells you more about confidence than about ability.
Things that throw a score off
Whatever test you pick, the conditions on the day can move your result by a few points. Lack of sleep and tiredness are the obvious ones. Doing a test half-distracted, with the TV on or on a bus, has the same effect, especially on timed questions.
A less obvious effect is repetition. Take the same test a second time and your score will most likely go up, because you're now used to the question types. That shows familiarity, not a jump in intelligence. It's also why clinical tests aren't repeated on the same person at short intervals. With an online test, treating your first attempt as the most realistic one makes sense.
Test anxiety is worth mentioning too. Someone who freezes in exams can score below what they're capable of. That's one advantage of an online test taken at a relaxed moment: nobody's watching and nothing is at stake.
Once you have a result
To read the number properly, you need to know where the average comes from. We cover the score bands, and what 115 or 130 actually means, in What Is the Average IQ?
It's also worth remembering what IQ covers: reasoning and problem-solving skills. It doesn't measure patience, creativity, getting along with people or seeing a job through. A good share of what matters in life sits outside that list.
If one area interests you in particular, you can look at it on its own. The N-back test targets working memory, the memory test short-term memory and the attention test focus. Short on time? The quick IQ test gives a rough picture in a few minutes. And if you just want to give your brain a workout without worrying about a score, have a look at the brain games.