People throw the word genius around constantly online and everyone seems to have a different threshold for what counts. Some say 140, some say 160, some say it is not about IQ at all. I want to know what psychometricians actually say about where genius begins and whether it is a real scientific category or just a cultural label we attach to people who impress us.
Genius is not a technical term in psychometrics and that is actually an important distinction 
The field uses giftedness which is typically defined as scoring in the top 2 percent, roughly 130 and above. Beyond that the labels get informal. Some researchers use highly gifted for scores around 145 and profoundly gifted for scores above 160 but these are not universally standardized cutoffs. The cultural concept of genius maps loosely onto the extreme right tail of the IQ distribution but also requires demonstrated exceptional creative or intellectual output, which IQ alone does not guarantee. History is full of very high IQ people who produced nothing remarkable and remarkable people whose IQ scores were never recorded or were surprisingly modest. Lewis Terman famously tracked hundreds of high IQ children in his longitudinal study and found that none of them produced work considered genuinely world changing, while several people he screened out including William Shockley went on to win Nobel prizes. High IQ is a necessary but not sufficient condition for genius level output 
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The scores above 160 that circulate online are almost always either fabricated or came from tests too poorly normed at the extremes to be meaningful 
Legitimate assessments have wide confidence intervals at the extreme right tail because the norming samples get very thin up there. Precise genius IQ claims should always be treated with skepticism.