Imagine you scored 115 on an IQ test. That number means nothing on its own. The real question is: 115 compared to what? An IQ score is not an absolute measure of intelligence. Instead, it is a relative measure that compares a person's result with peers in the same age group. In this article, we explain how this comparison works, where the baseline of 100 comes from, and what standard deviation means in simple terms.
Raw score and IQ score are not the same
The number of correct answers on a test is your raw score. You cannot interpret a raw score by itself because it depends on test difficulty and the total number of questions. An IQ score is that raw score converted into a statistical scale. The goal is not to show how many questions you got right, but where you stand compared to your peers.
Why is the average 100?
IQ scales traditionally use 100 as their midpoint. This is a standard convention: tests are calibrated so that the average performance of an age group equals 100. A score of 100 means exactly average. This standard became widespread through the Wechsler scales, which shaped modern intelligence testing. Results from our free IQ test also follow this 100-baseline model.
Standard deviation: What 15 points mean
Once you know the average, how far away are scores above or below 100? That is where standard deviation comes in. Most modern tests use a standard deviation of 15. This means:
- Between 85 and 115 (one standard deviation from the mean): About 68% of the population falls into this range. That is roughly two-thirds of all people.
- Between 70 and 130 (two standard deviations): About 95% of the population is in this range.
- 130 and above: Only about 2% of the population. This threshold usually marks entry into high IQ societies.
So a score of 115 is noticeably above average, but not rare. A score of 130, on the other hand, is quite uncommon. What matters most is not just the raw size of the number, but which percentile it represents.
Normal distribution and the bell curve
Behind all these percentages lies the normal distribution, also known as the bell curve. Most people cluster around the middle (around 100). As you move toward the extremes (very low or very high), the numbers drop quickly. That is why the 10-point gap between 100 and 110 represents a common shift, whereas the same 10-point gap between 140 and 150 represents a much rarer jump.
Why age matters
The same raw score can produce different IQ values at different ages. That is because scores are always compared within a person's specific age group. A child's performance is compared to children, and an adult's to adults. The old formula of "mental age divided by chronological age times 100" has largely been abandoned. It was replaced by age-group comparisons known as deviation IQ.
How online tests estimate scores
An online test is not normed on large sample populations like standardized clinical tests. Instead, it structures questions across a range of difficulty levels, factors in correct answers and timing, and scales the result to the standard 100-baseline model. We explain our scoring process on our methodology page. This type of result serves as a practical indicator, not an official clinical diagnosis.
How to view your score
In short: do not focus too much on a single number. An IQ score can shift by a few points depending on focus, fatigue, and testing conditions. What matters is your general range and how it compares over time. If you want to see sample questions, check out our article on IQ test sample questions and solutions, or try our free 28-question test to see where you stand.