Ahead of Apple’s third-quarter earnings report on July 19th, Fortune has tapped 39 analysts and has created a roundup of their iPad sales estimates. We already know that the iPad 2 has been flying off of store shelves since Apple announced the tablet on March 2nd. However, demand was so great that it’s unclear just how many Apple was able to manufacture and sell during the third quarter. Brian Marshall from Gleacher, Daniel Ernst from Hudson Square, and Mark McKechnie from Think Equity all estimate that Apple sold 6 million iPads during the quarter. That’s at the low-end of the analyst’s predictions. Amateur analyst Navin Nagrani suggested that the Cupertino-based firm sold 9.5 million iPads, but that’s still short of the 14 million iPad units sold that CLSA predicted last month. The average estimate of 7.92 million iPads sold is on a par with the Wall Street prediction of 7.72 million units, a 142% jump from the third quarter of 2010. Who’s right and who’s wrong? We’ll find out next Tuesday.