What does it mean to have a low IQ?

A 'low' IQ score is one significantly below the population mean — typically defined as below 70 (the 2nd percentile, two standard deviations below the mean). In clinical practice, an IQ below 70 is one of several criteria used in the diagnosis of intellectual disability, but it is not sufficient on its own. The DSM-5 and ICD-11 both require evidence of impairment in adaptive functioning across conceptual, social, and practical domains, in addition to a low cognitive score. A single online screener cannot diagnose anything. People with measured IQs in the 70s and 80s — the borderline and low-average bands — typically function adequately in everyday life with appropriate education, support, and practice.

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.