Then I created a class in CoD4, MW2 and MW3 that matched as closely as possible, and timed how long it took to walk across a map. So the relative size of Shipment, Killhouse and Rust is based on the walking speed being the same between each game.
I put all seven Face Off maps on the same page as a number of other maps, and I scaled them all to each other to give a good idea of their relative sizes. It's a large file so you may want to download it to see it better.
Intersection and Vortex are pretty much the same size as Dome. U-Turn and Getaway are the smallest of the Face Off maps, but Rust, Killhouse and Shipment are far smaller still.
While you're looking at the maps why don't you listen to some music by my man Prof: