How rare is an IQ of 109?

About 1 in 4 people score 109 or higher. That is 0.6 standard deviations above the mean of 100.

What does an IQ of 109 mean?

IQ tests are scored so that the population mean is 100 and one standard deviation is 15. About 68% of people score between 85 and 115, and 95% between 70 and 130. 109 sits in the "average" band. The number says where you rank on a test, not how your life goes.

Is an IQ of 109 good?

An IQ of 109 is higher than 73% of people, on a scale where 100 is the mean and 15 is one standard deviation. That is 1 in 4, and 0.60 standard deviations above the mean.

Percentile

73%

of people score below 109

IQ 109

AverageWAIS-IV descriptive band for 109. Newer manuals use softer words for the same ranges.

IQ 109 by group

Percentile

Normal curve, mean 100, SD 15
Group	Mean	Score below you	1 in X
Everyone, Wechsler scale	100	73%	1 in 4

Where the bands fall

Share of people in each WAIS-IV band, from the normal curve
Band	Scores	Share of people
Very superior	130+	2%
Superior	120 to 129	7%
High average	110 to 119	17%
Average	90 to 109	49%
Low average	80 to 89	16%
Borderline	70 to 79	6%
Extremely low	up to 69	2%

Percentile is the share of people who score below this IQ. “1 in X” counts the rarer side: people at or beyond this value above the median, at or under it below. IQ scores are normed to a normal curve by construction, so the percentile follows from the score alone.

What this means

In a school of 1,000 pupils, about 274 would score 109 or higher.
Mensa admits the top 2%, which is about 131 on this scale. 109 is 22 points short.
Online IQ tests are not normed on a population sample. A score from one of those is a guess in a confident font.

Questions

Is an IQ of 109 good?: An IQ of 109 is higher than 73% of people. That is the broad middle, where most people are. The WAIS-IV calls 90 to 109 "average".
How rare is an IQ of 109?: About 1 in 4 people score 109 or higher. That is 0.6 standard deviations above the mean of 100.
What does an IQ of 109 mean?: IQ tests are scored so that the population mean is 100 and one standard deviation is 15. About 68% of people score between 85 and 115, and 95% between 70 and 130. 109 sits in the "average" band. The number says where you rank on a test, not how your life goes.

Source: Wechsler scale definition: mean 100, SD 15 (WAIS-IV, Pearson 2008). Percentiles on this page are our estimate from a normal distribution with the stated mean and SD.

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