How to figure out the size of space for gfx card?

[SantiClaws]

I bought an ATI 5850 card not too long ago to replace a 5770 and had to do surgery on the case in order to get it in. The card itself fit, but there was no room for the power connector on the back due to the hard drives cage. I was thinking of having a dual card configuration, but that's not going to happen in this case due to lack of room. If I were to buy a case online, how would I make sure that there was plenty of room for a card?

 

[Kenmitch]

Most cases give specs for max video card length in mm's. Might not see it listed at the sellers.site but should be available at the manufacturers site. Same applies with video cards. 25.4mm = 1 inch.

 

[SantiClaws]

Thanks!