IQ scale: what the numbers mean and where you stand
The average IQ score on the scale is 100, with a standard deviation of 15 points. This means that about 68% of people have an IQ between 85 and 115, 95% between 70 and 130, and scores below 70 or above 130 occur in about 2% of the population on each side. These numbers are not arbitrary: the scale is designed so that the average is always 100, and tests are regularly renormalized for each new generation.
How the IQ scale works
IQ is not an absolute measure of mental ability but a relative position compared with other people of the same age. Technically, it is a standardized score: an individual result is converted into points according to how far it differs from the average.
The unit of this difference is the standard deviation (SD). One SD on the IQ scale equals 15 points. If your result is one SD above the average, your IQ is 115. Two SD above is 130. One SD below is 85.
The distribution of IQ in the population is close to normal, or bell-shaped. This is neither an accident nor a law of nature: tests are deliberately designed and calibrated to produce this distribution.
IQ ranges and what they mean
Different classification systems, such as the Wechsler scales, use slightly different labels for the ranges, but the numbers are the same everywhere. Below is the standard breakdown:
| IQ range | Description | Share of population |
|---|---|---|
| 130 and above | Very high | ~2% |
| 120–129 | High | ~7% |
| 110–119 | Above average | ~16% |
| 90–109 | Average | ~50% |
| 80–89 | Below average | ~16% |
| 70–79 | Low | ~7% |
| 69 and below | Very low | ~2% |
Half of all people on Earth fall within the 90–110 range. This is the norm in the statistical sense—not because it is somehow “right,” but because that is how the scale is constructed.
What a percentile is and why it is more intuitive
IQ 115 sounds abstract. The 84th percentile is more concrete: a person with that result scores higher than 84% of their age group. It is the same result, just expressed in a different way.
Here are a few reference points:
- IQ 100 = 50th percentile (middle)
- IQ 115 = 84th percentile
- IQ 130 = 98th percentile
- IQ 85 = 16th percentile
- IQ 70 = 2nd percentile
The percentile depends on the sample on which the test was normed. If a test was normed only on university students rather than the whole population, the numbers will differ. That is why it is important to understand how the test you use was constructed.
Why the average IQ is always 100, even across generations
This is no coincidence. Psychologists regularly restandardize tests: they take a new representative sample, observe how it solves the tasks, and adjust the norms. After this procedure, the average becomes 100 again.
That is why it is incorrect to compare the “raw” results of different years or different tests without considering the norming samples. If you took a test normed in 2000 and take the same test again today, your IQ may turn out a few points higher simply because the norms are outdated, not because your intelligence has actually increased. This phenomenon is called the Flynn effect: from one generation to the next, people on average perform better on tests.
What IQ measures—and what it does not
IQ reflects well what psychologists call general intelligence (the g factor): the ability for abstract thinking, working with patterns, analogies, and logical rules. These skills are indeed linked to academic achievement and a number of professional outcomes.
But IQ does not measure:
- Creative thinking—it is only partly related to intelligence
- Emotional intelligence—this is a separate construct
- Practical skills and professional experience
- Motivation, character, and social competence
Psychologists are cautious about sweeping claims such as “IQ determines destiny.” It is one predictor of many outcomes, but far from the only one and not the decisive one. A score of 95 versus 105 is a statistically insignificant difference in real life, even if it looks like a gap on paper.
How stable IQ is over time
In adults, IQ is relatively stable: the correlation between scores in youth and adulthood is about 0.7–0.8. This is high, but not absolute, stability. In children, results are less stable: a test at age 6 predicts the result at age 16 rather poorly.
Factors that can genuinely shift the result include:
- Education—several additional years of study produce a noticeable effect
- Serious illnesses or traumatic brain injuries
- Chronic sleep deprivation or prolonged stress
- Familiarity with the test format (practice can raise the score by a few points)
A one-time internet test is a guideline, not a diagnosis. Clinically meaningful IQ assessments are conducted by a specialist using a battery of standardized methods and take several hours.
If you want to get your own estimate right now, you can take the IQMeter test—it is free and gives an idea of your level relative to other users.
Frequently asked questions
Is IQ 100 good or bad?
100 is exactly the middle of the scale. Half of people score lower, half score higher. It is a neutral, completely normal result: that is how the scale is defined.
Can online IQ tests be trusted?
Quality varies greatly. A serious test should be normed on a representative sample and include enough items of varying difficulty. Short entertainment tests with 10–15 questions provide only a very rough estimate. Online tests are not suitable for clinical purposes.
Is it true that men and women have different IQs?
The average IQ of men and women is almost the same. The differences concern the profile rather than the level: men perform slightly better on spatial tasks on average, women on verbal ones. The spread of results is somewhat larger among men: at the extremes (very low and very high IQ), men are proportionally more numerous.
What does an IQ above 140 mean?
Such a result falls into the range sometimes called “genius,” occurring in about 0.4% of people, or four in a thousand. However, the precision of standard tests declines at the extreme ends of the scale: the items are simply not difficult enough to distinguish reliably between people in this range.
How does IQ change with age?
Processing speed and so-called fluid intelligence begin to decline gradually after age 30–40. At the same time, crystallized intelligence—accumulated knowledge and experience—continues to grow up to age 60–70. The overall IQ score in older adults is not necessarily lower if the test is age-normed, which standard adult scales are.