IQ scores are built around a simple framework: the average is 100, and most people score within 15 points of that number in either direction. That 15-point range is called a standard deviation, and it’s the key to understanding where any score falls relative to the general population. Once you know how the scale works, a raw number like 112 or 87 becomes much more meaningful.
How the Scale Works
IQ scores follow a bell curve, with 100 at the center. About 68% of people score between 85 and 115, meaning one standard deviation below and above the mean. Roughly 95% fall between 70 and 130 (two standard deviations), and 99.7% land between 55 and 145. So if you scored 115, you performed better than about 84% of the population. A score of 130 puts you ahead of roughly 98%.
The further a score sits from 100, the rarer it is. A score of 90 and a score of 110 are both common and well within the normal range. A score of 145 or 55, on the other hand, occurs in fewer than 1 in 1,000 people.
Common Classification Ranges
Different tests use slightly different labels, but the general categories look like this:
- 130 and above: Very superior, sometimes called “gifted.” This is the top 2% of the population and the threshold for Mensa membership on most Wechsler scales.
- 120 to 129: Superior.
- 110 to 119: High average.
- 90 to 109: Average. This is where roughly half the population falls.
- 80 to 89: Low average.
- 70 to 79: Borderline.
- Below 70: Extremely low. Scores around 70 to 75, combined with significant limitations in everyday adaptive skills, can support a clinical diagnosis of intellectual disability.
These labels describe statistical position on the curve, not a person’s worth or potential. A score of 95 and a score of 105 represent a trivial real-world difference, even though one falls just below the midpoint and the other just above.
Your Full-Scale Score vs. Index Scores
Most professionally administered IQ tests don’t just give you a single number. The Wechsler Adult Intelligence Scale, one of the most widely used tests, produces a Full-Scale IQ (FSIQ) along with four separate index scores: Verbal Comprehension, Perceptual Reasoning, Working Memory, and Processing Speed. Each index measures a different cognitive ability.
Verbal Comprehension reflects vocabulary, general knowledge, and the ability to reason with words. Perceptual Reasoning captures visual-spatial problem solving, like recognizing patterns in shapes. Working Memory measures your ability to hold information in mind and manipulate it, such as doing mental arithmetic. Processing Speed tests how quickly you can scan, sort, and identify simple visual information.
The full-scale number is useful as a summary, but the index scores often tell a more important story. Someone with a full-scale score of 105 might have a Verbal Comprehension score of 120 and a Processing Speed score of 85. That 35-point gap reveals a meaningful cognitive profile: strong verbal reasoning paired with slower processing. For understanding learning styles, identifying strengths, or diagnosing conditions like ADHD or learning disabilities, the pattern across indexes matters more than the single number at the top of the report.
Why the Same Score Can Mean Different Things
Not all IQ tests use the same scale. Both the Wechsler tests and the Stanford-Binet 5 use a mean of 100 and a standard deviation of 15, so their scores are roughly comparable. But older editions of the Stanford-Binet used a standard deviation of 16, which means a score of 132 on that older test is equivalent to about 130 on a Wechsler test. The Cattell scale uses a standard deviation of 24, so a Cattell score of 148 corresponds to a Wechsler score of 130.
This is why Mensa’s qualifying scores vary by test: 130 on the Wechsler scales, 132 on the Stanford-Binet, and 148 on the Cattell. They all represent the same percentile, roughly the top 2%, just expressed on different scales. If you’re comparing scores from two different tests, check which scale each one uses before assuming one is higher than the other.
The two major tests can also diverge at the extremes. Research comparing the Stanford-Binet and Wechsler scales in people with very low scores found that the Stanford-Binet tends to produce lower IQs than the Wechsler for the same individual, partly because the Stanford-Binet’s scoring extends further into the lower range. In one study, the average difference was nearly 17 points. This matters in clinical and legal contexts where a specific score threshold carries weight.
How Stable Is Your Score Over Time?
IQ scores become increasingly stable as you age, but they aren’t perfectly fixed. A study published in the Proceedings of the National Academy of Sciences tracked cognitive ability from early childhood into adulthood. Scores measured at ages 1 to 2 correlated only moderately with scores at age 29 (a correlation of about 0.31), meaning early childhood scores are rough estimates at best. By age 7, the picture gets much clearer. Scores at age 7 correlated strongly with scores at ages 16 and 29, with correlations ranging from 0.72 to 0.86.
In practical terms, if you were tested as a young child and scored 110, your adult score could reasonably land anywhere from the mid-90s to the mid-120s. If you were tested at age 10 or later, a retest in adulthood will typically fall within about 5 to 10 points of the original score. Day-to-day factors like sleep, stress, motivation, and familiarity with timed testing can also nudge a score by several points in either direction. A single test result is best understood as a range, not a pinpoint measurement.
What Scores Below 70 Actually Mean
A score below 70 does not automatically mean a person has an intellectual disability. The American Association on Intellectual and Developmental Disabilities requires three criteria: significantly limited intellectual functioning (generally an IQ around 70 to 75), significant limitations in adaptive behavior, and onset before age 22. Adaptive behavior covers everyday skills like managing money, following schedules, navigating social situations, and handling personal care.
Someone who scores 68 on an IQ test but lives independently, holds a job, and manages daily life without support would not meet the criteria. The score is one piece of a larger clinical picture, not a diagnosis on its own.
The Population Is Not Standing Still
IQ tests are re-normed every 15 to 20 years to keep the average at 100. This is necessary because raw scores have historically risen over time, a phenomenon called the Flynn effect. For most of the 20th century, each generation scored about 3 points higher than the previous one on standardized tests, likely driven by improvements in nutrition, education, and exposure to complex problem-solving environments.
Recent data complicates this picture. Some studies in developed nations have found that scores have plateaued or even declined slightly, a pattern called the reverse Flynn effect. The causes are debated and likely vary by country. What this means for you: a score of 100 today represents a slightly different level of raw cognitive performance than a score of 100 in 1980. If you’re comparing your score to a parent’s score from decades ago, the tests aren’t measuring against the same baseline.
Putting a Score in Perspective
IQ tests measure a specific set of cognitive abilities: reasoning, pattern recognition, working memory, processing speed, and verbal comprehension. They do not measure creativity, emotional intelligence, practical problem-solving in real-world contexts, motivation, or expertise in any domain. A person with an IQ of 115 who works persistently in a field for 20 years will almost certainly outperform someone with an IQ of 140 who doesn’t.
Scores are most useful when interpreted alongside their context. A psychologist reviewing your results will look at the spread between your index scores, compare your performance to your educational and occupational history, and consider whether any testing conditions (anxiety, fatigue, language barriers) may have affected the outcome. If you’ve received a score and aren’t sure what to make of it, the most informative part of the report is usually not the number at the top but the pattern of strengths and weaknesses in the subtests beneath it.