American movie posters come in a wide array of sizes and styles. Here are some examples of the more common sizes.

The one sheet is the most common movie poster size. Up until 1984 or so, one sheets were 27x41, while after that they 27x40.

A half sheet is usually one half the size of a one sheet - or around 22x28 inches - and are printed on card stock.

Folding - While some older posters from movie companies were folded, the typical way to send them now is rolled into a tube.