Alfred Binet, a French psychologist, is credited with being the inventor of the first modern IQ test. Later American tests posited that intelligence was fixed and unbending. This did not agree with his conceptualization of intelligence.

The very concept of an Intelligence Quotient (IQ) is controversial. However, it remains useful for trying to make sure kids get an appropriate education for their needs. That was really the goal with which Binet was tasked, so it seems fitting that this is the essence of his legacy.

IQ Score Range Distribution

IQ Range ("Deviation IQ")IQ Classification
145-160Very gifted or highly advanced
130-144Gifted or very advanced
110-119High average
80-89Low average
70-79Borderline impaired or delayed
55-69Mildly impaired or delayed
40-54Moderately impaired or delayed
IQ tests are designed to conform to a Bell Curve distribution. This means if you graph them, they make a nice shape that is high in the middle and tapering on both ends that looks a bit like a bell as you can see in the image below.

iq distribution curve

IQ tests are designed to use 100 as the normed average score. In fact, half of all IQ scores fall between 90 and 110. The standard deviation for an IQ score is 15 points. So, 70 percent of all IQ scores fall between 85 and 115 points. Note how this means they fall within one standard deviation of the norm.

Next, 95 percent of all scores fall within two standard deviations, or plus or minus 30 points. So most people will have an IQ between 70 and 130. Last, 99.5 percent of all people have an IQ between 60 and 140.

Generally speaking, an IQ between 115 and 130 is considered “normal gifted” or “moderately gifted.” These are the kinds of kids you typically see in school enrichment programs, gifted classes and so forth. IQs above 130 are very gifted and typically require more accommodation than your run of the mill enrichment program. They are more likely to be grade skipped, attend college early and so forth.

For more detailed information about specific IQ scores, refer to the following pages:

What is a genius level IQ?

Although some sources say that genius level IQ starts around 140 or 145, the reality is that most IQ tests only reliably test up to 140 or 145 IQ. It takes special assessment by qualified professionals to test IQs above that.

For evidence of this, you don’t need to look any further than Richard Feynman. He is widely considered to be one of the geniuses of his era, yet he took some glee in reporting that his high school IQ test score was merely 125. He declined to join Mensa on the excuse that his IQ wasn’t high enough.

Meanwhile, he won the Putnam by a wide margin. The Putnam is a rigorous math competition that awards scholarships. It has been suggested that his high school IQ test must have been a strongly verbal test that gave short shrift to mathematics.

It gets even more complicated if you have a child who is bright but has special needs or a learning disability. These children are often called “twice exceptional,” which is sometimes abbreviated 2xE. Their strengths can mask their weaknesses while their weaknesses hide their strengths. Without special testing, they may appear to be average in terms of school performance while being simultaneously bored and frustrated.

For people who have been very frustrated, testing can be useful for identifying exactly what is going on. Having their strengths and weaknesses mapped out can be very refreshing and empowering. This may be the strongest argument for continuing to have and use IQ tests, regardless of their many shortcomings and the controversy that swirls around them.

If you get a score that you feel is too low and you feel doesn’t really represent your ability, it might be best to assume you need more testing. In some sense, that worked for Richard Feynman and he went on to have a wildly successful career.