The split for domestic box office works on a sliding scale. The studio's cut is very high in the first week and then steadily drops week by week. The studio usually ends up with 50-55% of domestic box office, although for some films it can be higher or lower depending on the specific deals with theatres and how frontloaded their box office runs are. I read one entertainment journo who claimed some deals are now straight 50/50 or 55/45 splits all the way through, but I never saw that confirmed elsewhere.
The studio gets less from foreign box office, typically about 40% across the board, although China sets the rate at a much lower 25%. If you want a detailed account of all of this and how the studios often don't cover total costs from box office receipts alone, even on films they consider to be successful, with home entertainment revenue being an integral part of overall profitability, then read Edward Jay Epstein's The Big Picture
. He's an investigative journalist who looked into the studios' modern business model.