Apple has started taking pre-orders for its iPad gadget.

Estimates in the US on the first day of pre-sales have suggested over $75 million in revenue has already been more than achieved.

With only three weeks to go before the release of the iPad, people are buying the product unseen, with very few having gone on display.

With so many pre-orders, it has been estimated that Apple will need to manufacture anything up to one million iPads before the end of April.

In the US, the least-expensive 16 GB model will cost $499.