What is the highest IQ ever recorded?

Claims about 'the highest IQ ever' are essentially marketing rather than science. The reliability of any test at the extreme tails of the distribution is poor: the standard error of measurement at IQ 160 is much larger than at IQ 100, and most tests have a low ceiling that pins all extreme test-takers at the maximum reportable score. Marilyn vos Savant's reported IQ of 228, William James Sidis's reputed IQ of 250 to 300, and Christopher Langan's reported IQ of 195 are all based on tests with documented validity problems at the extremes. Modern psychometricians treat any IQ above about 160 as 'in the very superior range' rather than as a precise number. The Guinness Book dropped its 'highest IQ' category in 1990 specifically because the records could not be validated.

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.