IQ Articles > Normal IQ score

Normal IQ score

IQ scores are all too often misunderstood. What is a normal IQ score? What is a high IQ score? Those are the most common questions regarding IQ tests. Here are the methods you can use to recognize normal and high IQ test scores.

Original IQ score calculation

Initially, IQ scores were expressed as a ratio of one’s mental age (MA) to one’s chronological age (CA), multiplied by 100 to get rid of the decimal point: IQ = MA/CA x 100. The normal IQ score was 100, which meant that your mental and chronological ages coincided. A score above 100 meant that your mental age was higher than your chronological age. Each test would usually provide some kind of a classification table to help you interpret you score.

Modern IQ test scores

Psychologists today no longer use the above formula to calculate IQ test scores. Instead, modern intelligence tests apply statistical methods to produce a score reflecting one's performance as compared to the average performance of his peers (1). The normal IQ score is still 100, meaning that the average score people get is 100. That happens because IQ test scores have a so-called “normal” distribution. In a normal distribution, most of the values cluster around the average with few values that differ significantly from it. That creates a bell shaped curve, known as the IQ bell curve, which is illustrated below.

IQ bell curve

IQ score percentiles

Another way for interpreting your IQ score meaning is in terms of its percentile rank. A percentile rank shows the percentage of people that scored above and below a certain score. For example, if your score falls in the 85th percentile, it means that 85 percent of the people that took the test got lower scores, and 15 percent (100% - 85%) got higher scores. A normal IQ score is in the 50th percentile, and a high IQ score is roughly one in the 95th percentile and above. The following table will help you interpret some popular IQ scores (2):

IQ Score

Percentile Rank

IQ Score

Percentile Rank

IQ Score Percentile rank
155 99.988 118 88.5 81 10.3
154 99.984 117 87.1 80 9.1
153 99.979 116 85.7 79 8.1
152 99.974 115 84.1 78 7.1
151 99.966 114 82.5 77 6.3
150 99.957 113 80.7 76 5.5
149 99.946 112 78.8 75 4.8
148 99.93 111 76.8 74 4.2
147 99.91 110 74.8 73 3.6
146 99.89 109 72.6 72 3.1
145 99.87 108 70.3 71 2.7
144 99.83 107 68.0 70 2.3
143 99.79 106 65.5 69 1.9
142 99.74 105 63.1 68 1.6
141 99.69 104 60.5 67 1.4
140 99.62 103 57.9 66 1.2
139 99.53 102 55.3 65 1.0
138 99.44 101 52.7 64 0.82
137 99.32 100 50.0 63 0.68
136 99.18 99 47.3 62 0.56
135 99.02 98 44.7 61 0.47
134 99.83 97 42.1 60 0.38
133 98.61 96 39.5 59 0.31
132 98.36 95 36.9 58 0.26
131 98.06 94 34.5 57 0.21
130 97.7 93 32.0 56 0.17
129 97.3 92 29.7 55 0.13
128 96.9 91 27.4 54 0.11
127 96.4 90 25.2 53 0.09
126 95.8 89 23.2 52 0.07
125 95.2 88 21.2 51 0.054
124 94.5 87 19.3 50 0.043
123 93.7 86 17.5 49 0.034
122 92.9 85 15.9 48 0.026
121 91.9 84 14.3 47 0.021
120 90.9 83 12.9 46 0.016
119 89.7 82 11.5 45 0.012

IQ classification tables

Additionally, each IQ test offers you a classification table. A normal IQ score ranges between 90 and 109. As shown in the following table, scores over 120 are considered high. The following can be used as a general guideline(3):

IQ Range

WAIS-III/WISC-III

Percent of population

130+

 Very superior

2.2

120-129

 Superior

6.7

110-119

 High average

16.1

90-109

 Average

50.0

80-89

 Low average

16.1

70-79

 Borderline

6.7

69 and below

Extremely low/intellectually deficient

2.2

In conclusion, a normal IQ score is 100. A high IQ score is a score roughly over 120. You should also look at your score's percentile rank and the interpretation table provided after each test.

___________________________________________________________________________________________

References:

  1. Jensen, Arthur R. Straight Talk About Mental Tests. New York: The Free Press, 1981. 4-6.
  2. American Psychiatric Association. Diagnostic and statistical manual of mental disorders (4th edition, text rev.). Washington DC, 1994
  3. Wechsler, David. WAIS-III Administration and Scoring manual. San Antonio, TX: Psychological Corporation, 1997
LATEST IQ NEWS
March 26, 2007
1940s IQ tests help reveal how lifestyle affects our brain
IQ tests carried out on about 70,000 Scottish children in 1947 are helping scientists discover how our lifestyle affects our mental abilities. The findings suggest that smoking, obesity, poor diet, and the lack of physical exercise...
Read full story
March 22, 2007
Gifted students listen to Heavy Metal as a way to handle peer pressure
A group of scientists at the University of Warwick, who conducted a study on 1,057 students between the ages of 11 and 18 regarding their views on family, education and free time, suggests that gifted students may be listening to Heavy Metal music...
Read full story
March 21, 2007
Humans are able to detect “impossible” objects from an early age
We’ve all been baffled by drawings of so-called impossible objects – like staircases leading to nowhere and fountains starting and ending at the same place. But when do we develop the ability to detect...
Read full story
To see all IQ news to date, click here!