Over 140 - Genius or almost genius
120 - 140 - Very superior intelligence
110 - 119 - Superior intelligence
90 - 109 - Average or normal intelligence
80 - 89 - Dullness
70 - 79 - Borderline deficiency in intelligence
Under 70 - Feeble-mindedness

Normal Distribution of IQ Scores

50% of IQ scores fall between 90 and 110
70% of IQ scores fall between 85 and 115
95% of IQ scores fall between 70 and 130
99.5% of IQ scores fall between 60 and 140

Low IQ & Mental Retardation

An IQ under 70 is considered as "mental retardation" or limited mental ability. 5% of the population falls below 70 on IQ tests. The severity of the mental retardation is commonly broken into 4 levels:

50-70 - Mild mental retardation (85%)
35-50 - Moderate mental retardation (10%)
20-35 - Severe mental retardation (4%)
IQ < 20 - Profound mental retardation (1%)

High IQ & Genius IQ

Genius or near-genius IQ is considered to start around 140 to 145. Less than 1/4 of 1 percent fall into this category. Here are some common designations on the IQ scale:

115-124 - Above average
125-134 - Gifted
135-144 - Very gifted
145-164 - Genius
165-179 - High genius
180-200 - Highest genius

The Average on an IQ Scale

The scoring of an IQ test is not the same for everyone, because age is used in determining a score. Intelligence quotient is determined by the "intelligence age" (I A) in relation to the chronological age of the person being tested. IQ scales can differ from each other (Americans use scales with IQ values above 200), but the mean value of most scales is an IQ of 100. This represents normal intelligence.

Think you are smart? Well, if your IQ is 130, that puts you ahead of 98% of people. Of course that means there are still 120 million people who are smarter than you (the other 2%). Also, recent research shows that a person's level of self-discipline is more predictive of success than their IQ level. In other words, don't take too much meaning from your score on an IQ scale.