IQ Score Chart: IQ Ranges, Percentiles & the Bell Curve

An IQ score gets much easier to read once you stop looking at the number alone. The chart below translates the familiar 100-centered scale into standard deviations and percentiles — the two pieces that reveal how common or unusual a score actually is.

A score of 130 sounds only 30 points higher than 100. Statistically, the gap is much more informative: on an IQ scale with a mean of 100 and a standard deviation of 15, 130 sits two standard deviations above the center and lands around the 98th percentile. Roughly 2 people out of 100 score at or above that point under the familiar normal-curve model. If you want that rarity translated more precisely, see what percentage of people have an IQ of 130 or higher.

That is the job of an IQ score chart. The IQ number gives you the scale position; the percentile tells you how that position compares with the reference population. If you want the foundation underneath the number first, see what an IQ score actually means and why the average IQ is 100.

IQ Score Chart

These percentiles are approximate values from a normal distribution with mean 100 and standard deviation 15. The APA Dictionary of Psychology, for example, lists 100 and 15 as the mean and standard deviation for Stanford–Binet Full Scale IQ scores. Other tests and editions can use their own norms and interpretive conventions, so the chart is a guide to the familiar 100/15 scale rather than a substitute for a specific test manual.

IQ Ranges in Standard-Deviation Bands

The cleanest way to understand IQ ranges is to count distance from 100 in 15-point steps. Each step is one standard deviation. Under a normal-curve approximation, about 68% of scores fall within one standard deviation of the mean, and about 95% fall within two.

You will see labels such as “average,” “high average,” “superior,” “very high,” or “gifted” attached to ranges on different websites and reports. Those labels are not universal units. Test publishers, clinicians, schools, and gifted programs can use different cutoffs and wording. The standard score, percentile, and the norms behind the test carry more information than a loose adjective.

What Does the IQ Bell Curve Show?

The bell curve is useful because it makes rarity visible. Scores pile up near 100 and thin out toward both tails. The curve is a statistical model, not a photograph of every real dataset. Population data can depart somewhat from perfect normality; one large study of general-intelligence scores, for example, found meaningful departures from a normal distribution. That analysis by Johnson and colleagues is a useful reminder to treat the curve as a practical map.

Why Percentiles Get Strange Near the Ends

Here is the part of the chart that often surprises people. IQ points are evenly spaced. Percentiles are not.

Moving from IQ 100 to 115 is a 15-point jump: one standard deviation. On the normal curve, that moves you from the 50th percentile to roughly the 84th — about 34 percentile points. Moving from IQ 130 to 145 is also a 15-point jump, yet it moves you from roughly the 97.7th percentile to the 99.9th — only a little over 2 percentile points.

The reason is simple: percentiles crowd together in the tails. There are fewer people left to pass. This is why “15 IQ points” and “15 percentile points” are completely different ideas.

Percentiles are still extremely useful because they answer the question readers usually care about: how common is this score in the norm group? A review by Crawford and Garthwaite argues for reporting percentile ranks alongside standardized neuropsychological scores precisely because percentiles make relative standing tangible.

Why an IQ Score Is Never as Exact as the Chart Looks

A chart can print 97.7th percentile with a decimal place. A real person’s measured score is less crisp. Psychological tests have measurement error, normative samples have uncertainty, and professional reports often use confidence intervals around observed scores. A score of 130 should not be imagined as a pin driven permanently into exactly the 97.724986th percentile.

Research on percentile norms has emphasized this uncertainty directly. Crawford, Garthwaite, and Slick showed why percentile estimates from normative samples also carry uncertainty and proposed ways to report it. The chart is best used for orientation: it tells you the neighborhood of a score, not its GPS coordinates.

What the Chart Cannot Tell You

Two people can have the same overall IQ score and arrive there through different cognitive profiles. One might be strongest in verbal knowledge and slower on processing-speed tasks; another might show the reverse pattern. An overall score compresses that shape.

It also says little about abilities that the assessment does not directly measure. Our guide to fluid vs crystallized intelligence shows how even cognitive ability contains distinct dimensions, while IQ vs EQ explains why emotional intelligence belongs to a different conversation.

Try an IQ-Style Score Yourself

If you want to experience the kinds of verbal, logical, and visual-spatial questions associated with IQ testing, Cognitive Train’s free IQ-Style Test gives you a score plus a six-skill breakdown. Its result uses the site’s own transparent IQ-style scoring system and is designed as an online reasoning challenge. It is not a professionally normed clinical IQ result, so use it as a snapshot of performance on these question types.

How to Read Any IQ Score in Five Seconds

Start at 100. Count 15 points for every standard deviation. Then translate the position into a percentile if you want to know how common the score is. That three-step habit turns an IQ number from an isolated label into a location on a population scale.

For more context, browse the Brain Articles collection, explore Cognitive Train’s brain tests and cognitive assessments, or use the cognitive training and brain training tools to examine individual mental skills directly.