What is the average IQ by age?

Modern IQ tests are age-normed, which means a 30-year-old and a 70-year-old who both score IQ 100 are not solving the same problems at the same level — they are both performing at the median for their age band. Raw cognitive performance changes substantially across the lifespan: fluid abilities (matrix reasoning, processing speed, working memory) peak in the late teens to mid-twenties and decline slowly thereafter, while crystallized abilities (vocabulary, general knowledge) rise through middle age and remain largely intact into old age. The age-norming convention means that 'average IQ' is always 100 within an age band, regardless of the actual cognitive performance level. If you compare your child's age-normed IQ to your own across decades, you are comparing relative position within different distributions, not raw cognitive ability.

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.