What is a genius-level IQ?

There is no agreed-upon clinical or scientific definition of 'genius' that maps cleanly to a specific IQ cutoff. The popular folk definition typically places it somewhere between 140 and 160, but these numbers are essentially arbitrary. Lewis Terman's longitudinal study of high-IQ children, begun in the 1920s, used a cutoff of IQ 135 to identify 'gifted' subjects; many of his subjects went on to distinguished careers, but none won a Nobel Prize, while two children rejected from the study (William Shockley and Luis Alvarez) later did. The lesson is that exceptional cognitive ability is one input to exceptional achievement, but it is not sufficient and the threshold for 'genius-level' performance varies by domain. Mensa requires the 98th percentile (roughly IQ 130); the Triple Nine Society requires the 99.9th percentile (roughly IQ 146); the Mega Society requires the 99.9999th percentile. Each successive cutoff identifies a smaller and statistically less reliable group.

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.