how many Americans have seen avatar?

Let's give up on that question and focus on a simpler one -- how many tickets have been sold in the U.S. to see Avatar? If you search for this online, you'll always come down to Box Office Mojo's numbers -- everyone just cites them. They say 93 million tickets, based on revenue of 709 million and an average ticket price of $7.61. This might work for most movies, but for Avatar it's obviously crap. The average ticket price for Avatar needs to be adjusted to include IMAX and 3d showings. Box Office Mojo, while not doing this, helpfully has an article about the breakdown of Avatar's ticket sales: around 64% 3D, 16% IMAX, and 20% 2D. The average price of an IMAX ticket is $14.58, and the article guesses that there's a $10 average price for 3D tickets. 709m/(.64*10+.16*14.58+.20*7.61) is around 69.1 million tickets. This puts it somewhere around Independence Day, Spider Man, and Love Story in number of tickets sold. Note that other movies' ticket totals on Box Office Mojo's list should be correctly calculated because they don't have these large 3D and IMAX components. For future reference, the "real" average price for an Avatar ticket, given Box Office Mojo's prices and breakdowns, is $10.25. So as a rough approximation, just divide Avatar's gross ticket sales revenue by 10 to get the actual number of tickets sold.