It is 1:1.
Stargate wiki's are written by fans, and fans speculate a lot. Officially, the BC-304's size was never stated.
Fans thought; It's a carrier in space. How big is an aircraft carrier ship today? 200+ meters. Huh, so the 304 must be 200+ meters too?
Wrong! The front halves of the wings have to contain all the fighters, with the rear halves housing sizeable engines. Thus, each wing alone must be the size of an aircraft carrier!
We tried a 220 meter build. We could barely squeeze 2 1:1 scale F-302s inside, with the wing having no frontal wall and no interior walls. It needs to be able to hold 8 per wing.
Even so, I still had to build the fighters with 4 meter less wingspan than stated in said wikis. They just wouldn't fit nicely.
So believe me when I say, it's as close to one on one scale as it'll get.