The IQ Scale — what does a score of 100, 115, 130, or 145 mean?

You tell someone your IQ is 115, and you see the question in their eyes: "Is that high or low?". The IQ scale is one of the most frequently cited measures in psychology — and one of the least understood. This guide explains it from the ground up: what each score actually means, why the average is 100, how to calculate percentiles, and what the typical classification ranges look like.

Where the IQ scale comes from

The first intelligence scale was developed by French psychologist Alfred Binet in the early 20th century. His goal wasn't to "measure genius" — he wanted to identify children who needed additional school support. Binet introduced the concept of "mental age" — a child who solves problems typical of 10-year-olds has a mental age of 10, regardless of biological age.

The term intelligence quotient (IQ) was coined by German psychologist William Stern. His formula was simple:

IQ = (mental age ÷ biological age) × 100

A 10-year-old with a mental age of 12 had an IQ of 120. This model worked well for children, but didn't work for adults — because "mental age" stops growing linearly after about age 16.

That's why since the 1930s we use deviation IQ, proposed by David Wechsler. This is today's standard.

How the modern IQ scale works

The modern IQ scale has two key parameters:

• Mean (μ) = 100 — the average score in the population
• Standard deviation (σ) = 15 — a measure of how scores "spread out" around the mean

Scores are distributed according to a Gaussian curve (normal distribution). This means:

• About 68% of the population scores between 85–115 (± 1 standard deviation)
• About 95% falls within 70–130 (± 2 standard deviations)
• About 99.7% falls within 55–145 (± 3 standard deviations)

In practice: if you pick 100 random people, about 68 of them will have IQ between 85 and 115. Only about 2 will have IQ above 130, and 2 will have IQ below 70.

IQ classification — what each range means

There are several classifications in use. The most commonly cited are from the Wechsler tests (WAIS-IV, WISC-V), used by most psychologists worldwide.

Below average (< 85)

IQ 70–84 — borderline low intelligence

This range includes about 14% of the population. People with scores in this range may have difficulties with more complex academic tasks but function fully in daily life. A score of 70 is the lower boundary of "normal" — below that begins the area of clinical diagnosis.

IQ below 70

A score below 70 (2 standard deviations below the mean) is a psychometric criterion that, in a clinical context, may require additional diagnosis. An IQ test alone is not sufficient for any diagnosis — a full psychological evaluation is required.

Average (85–115)

This is where most of the population is — about 68%.

IQ 85–99 — low average / below average

A perfectly healthy, typical range for many professions and social roles. Life success for people with these scores depends much more on personality traits (conscientiousness, perseverance) and social context than on "IQ alone."

IQ 100 — average

This is a typical score. If you invited 100 random people off the street, the median of their results would be close to 100. A score of 100 doesn't mean "average" in a negative sense — it means your cognitive abilities are consistent with most of the population.

IQ 101–115 — high average

This is where the quarter of the population above average begins. People with IQ 110-115 usually do well in university studies, although this is not guaranteed.

Above average (116–129)

About 14% of the population.

IQ 116–129 — above-average intelligence

This range includes typical university graduates and specialists who need abstract thinking (engineers, doctors, programmers, scientists in less theoretical disciplines).

High and very high intelligence (130+)

IQ 130 — Mensa threshold

This is the famous 2 standard deviations above average mark. A score of 130 corresponds to the 97.7th percentile — in other words: only about 2.3% of the population scores 130 or higher.

Mensa International — the international high-IQ society — uses the top 2% of the population as its membership criterion. That criterion corresponds to a score of 130 on the Wechsler scale (or other scores, if the test has a different σ).

IQ 145+ — very high intelligence

A score of 145 is 3 standard deviations above the mean — approximately the 99.87th percentile. Only 1 person in 750 scores 145 or above. This is the level that meets the entry criteria for more restrictive high-IQ societies like Intertel (99th percentile threshold).

IQ 160+ — exceptional

A score above 160 (4 standard deviations) is theoretically 0.003% of the population — one person in ~30,000. In practice, IQ tests in this range already have low reliability: they're based on very small normalization samples, and the score's confidence interval widens. Every standard IQ test has an effective ceiling of about 155–160; above that, specialized high-range IQ tests are needed, whose reliability is debatable.

Percentile — a more intuitive measure

Although psychologists mainly operate with the IQ scale, percentile is more intuitive for most people — that is, the answer to "What percentage of the population has a lower score than mine?"

Conversion examples:

Percentile is derived directly from the normal distribution — it's simply the area under the Gaussian curve to the left of your score.

What the IQ scale does NOT measure

All the numbers above describe general intelligence (the g factor), most often measured through abstract reasoning tasks, pattern analysis, and working memory. But there are concepts the classical IQ scale doesn't cover:

• Emotional intelligence (EQ) — understanding your own and others' emotions
• Creativity and divergent thinking — generating multiple solutions to problems
• General knowledge and erudition — your IQ score doesn't depend on what you've read
• Conscientiousness, perseverance, self-discipline — personality traits
• Practical intelligence ("street smarts") — handling everyday situations

Much research suggests that conscientiousness and perseverance (grit) are equally — and sometimes more — powerful predictors of life achievement than IQ alone.

Can IQ be changed?

Short answer: slightly. The g factor, or general intelligence, is largely stable in adulthood — especially fluid intelligence (the ability to solve new problems). What you can realistically improve through learning and experience is crystallized intelligence — knowledge, vocabulary, familiarity with strategies for solving specific problems.

Training in solving test tasks will improve your IQ test score — but not necessarily intelligence itself. This effect is called test-retest effect or practice effect and typically improves the score by 3–8 points after taking similar tests several times.

Most common errors in IQ interpretation

"A score of 145 means I'm twice as smart as someone with 72."

No. The IQ scale is not a proportional scale. A score of 100 isn't "twice as good" as 50. It's an ordinal scale arising from the normal distribution — it only says where you stand relative to others, not how much "more intelligence" you have.

"A child with IQ 110 is smarter than an adult with IQ 105."

You can't compare IQ across age groups. A child's score is compared to other children of the same age, while an adult's score — to other adults. These are two different reference groups.

"I got 132 IQ on an online test — so I qualify for Mensa."

No. Official Mensa requires a test administered under the supervision of a certified administrator. Online tests — including ours — are educational and entertainment aids. Real qualification requires an official examination by a psychologist or at a Mensa exam.

Summary

The IQ scale isn't simply a "smartness number" — it's a statistical way of mapping your cognitive abilities relative to the rest of the population. The mean is 100, most of the population falls between 85 and 115, and the 130 threshold corresponds to the top 2% (Mensa criterion).

Regardless of what score you get on a test, remember:

• IQ is one of many dimensions of intelligence — it doesn't measure emotion, creativity, or perseverance
• An online test is an approximation — differences of ±10 points are normal
• Life success depends on many factors — IQ is one of them, but not the most important

If you want to check your score, try our free test — with instant results and full interpretation.

Sources

• Wechsler, D. (2008). Wechsler Adult Intelligence Scale — Fourth Edition (WAIS-IV).
• Hunt, E. (2011). Human Intelligence. Cambridge University Press.
• Deary, I. J. (2020). Intelligence: A Very Short Introduction. Oxford University Press.
• Mensa International — official website