How We Calculate Your IQ Score

CheckIQ Editorial Team · Updated

Every test is generated fresh, and each question has a difficulty level from 1 to 5. Your score is the ability level that best explains which questions you got right and which you missed, placed on the standard IQ scale (mean 100, standard deviation 15). Your percentile comes from the normal distribution. The result is an estimate, not a clinically normed score.

Which questions are used?

The test uses non-verbal questions that are common in intelligence research: matrix reasoning, number series, figure series and odd-one-out problems. They use shapes and numbers instead of words, so they work the same way in every language. The full test has 36 questions and the quick test has 15.

The questions are generated fresh for every attempt. Each one follows a rule (for example “the shape changes by row, the count by column”) with randomly chosen shapes, numbers and rotations, and questions you have already seen are skipped. Retaking the test gives you a new test, so remembering answers doesn’t help.

How is the score calculated?

Each difficulty level has a known position on the IQ scale. The test then finds the ability level that best explains your pattern of right and wrong answers. This is the item-response approach used by modern adaptive tests. Getting a hard question right counts for more than getting an easy one right, and a lucky guess counts for less, because every question can be guessed.

That is why the easy, medium and hard tests all land on the same scale. A perfect score on the easy test is good, but it can’t prove a score far above 120. Skipped questions count as wrong.

The result is rounded and kept between 55 and 145, the range an online test can estimate sensibly.

How is the percentile calculated?

IQ scores follow a normal distribution with a mean of 100 and a standard deviation of 15. Your percentile is the share of that distribution below your score. For example, 115 is higher than about 84% of people.

What are the limits?

  • The test hasn’t been normed on a large, representative sample the way clinical tests have.
  • Tiredness, distraction and guessing can move a score by several points.
  • It measures reasoning with shapes and numbers, not every kind of intelligence.
  • It can’t be used for diagnosis, school placement, hiring or Mensa admission.

What happens to your answers?

Nothing leaves your device. Scoring happens in your browser, and your last result is saved only in your browser’s local storage.

Frequently asked questions

Is the CheckIQ score a real IQ?

It’s an estimate on the same scale as real IQ scores (mean 100, SD 15). It isn’t a clinical measurement.

Why is my score capped at 145?

An online test can’t tell very high scores apart reliably, so it stops at 145 rather than guess.

Will I get the same questions if I retake the test?

No. Every test is generated at random, and questions you have already seen are avoided, so each attempt is a new test.

Learn more about IQ