Apple will sell more than one million new iPads on Friday, the day the device goes on sale, according to one analyst.

Gene Munster of Piper Jaffray believes that Apple will generate at least $650m on the day, assuming an average sale price of $650, reports Business Insider.

He arrived at these figures by looking at the past history of iPad launches and also the launch of the iPhone 4. Apple sold 300,000 units of the original iPad on launch day.

With the iPad 2, supply constraints meant that the company didn't open up pre-orders until early in the morning of the first day of sale, with many outlets selling out very quickly. Shipping estimates moved from 3-5 days to 2-3 weeks very quickly, Munster noted.

However, Apple didn't ever release a first-day figure for iPad 2 sales, probably because the supply constraints would have made the number "artificially" low, Munster believes.

With the iPhone 4, Apple took 600,000 pre-orders in one day before systems were overloaded and pre-orders brought to a halt. Within three days of retail sales beginning, Apple had sold 1.7 million iPhone 4 units. Given that the new iPad is due to go on sale in 12 countries on Friday - the iPhone 4 was only initially available in five - "we are confident the company will sell over 1m on launch day," Munster says.

As the article points out, though, Munster has been wrong with iPad sales estimates before - with the launch of the original iPad, he reckoned Apple would sell between 600,000 and 700,000, more than twice the actual figure.