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I did a lot reading last night about IV. Found a great article at http://www.optionsplaybook.com/options-introduction/what-is-volatility/ . I found it very helpful understanding what the percentages stand for. Another place I found a different IV number on IB was chart preferences on the underlying stock. If you click on a STOCK chart you'll see a box that allows you to graph "option Implied volatility. I'm just trying to put all the different IV numbers into the proper perspective. Is there an article on SO that I missed??