What is the average IQ?

By construction, the average IQ on any modern test is 100, with a standard deviation of 15. This is a definitional property of the test, not an empirical finding: when test publishers norm a new IQ battery, they convert raw scores to standard scores so that the mean of the norming sample equals 100 and the standard deviation equals 15. About 68% of adults score between 85 and 115, about 95% between 70 and 130, and about 99.7% between 55 and 145. Reports of 'national average IQ' that differ from 100 are typically the result of comparing one country's mean to another country's norming sample — the comparison is informative only if you know which sample is the reference. Within any given country normed sample, the mean is 100 by definition.

This question comes up frequently from users of free online IQ tests and from people considering whether to pursue a clinical evaluation. The full answer depends on context — what the score will be used for, how recently the test was administered, and what other information is available. The brief answer above captures the broad consensus from the published research literature; the linked deep-dive articles cover the underlying evidence in more detail.

Related considerations include the standard error of measurement on the relevant test, the population the test was normed against, and the specific cognitive abilities the test samples. A score is much more informative when interpreted alongside these contextual variables than when reported as a bare number.

If this answer raises further questions, see the related FAQ entries listed in the sidebar and the longer-form articles on the same topic in the article library. The site is designed to provide layered depth: the FAQ entries offer concise answers, the deep-dive articles offer the underlying research, and the score-interpretation pages tie the abstract concepts to specific result bands.