• depends on the test, some only go so far. most recognised tests top out at either 160 or 180 though there is some debate as whether there is much point measuring past 150 as the tests become more inaccurate above that number. by the way mines 169 on a test i did at school, i did one online once too and it came back with "we can't measure your IQ as you answered every question right" but i think i may have lost several braincells since then.
• A standard calibrated IQ test has a mean score of 100 (so an IQ of 100 really means average) and depending on the calibration method, it has a standard deviation of 15. That would mean that 68% of people are within the range 85 to 115. The top 1% of the population would get 135 or higher. There is no upper limit to the theoretical IQ using this method, but it becomes increasingly unlikely. For instance an IQ of 200 would happen about once in 76 billion tests. (5 billion if stddev=16) If you see scores quoted above 200, they are not using a calibrated test.
• IQ stands for Intelligence Quotient. It's the measure of an individual's mental age divided by their physical age times 100 percent. Theoretically, there is no limit. On a practical side, if a 5 year old had the knowledge of a 100 year old, his IQ would be 2000.
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