How big is Bainbridge Island?

About 28 square miles of land. The city fills the whole island.

That is large enough that Winslow is walkable and Bloedel is not. Drive times from downtown are on the order of 10–15 minutes to Grand Forest, Fay, Battle Point, and Fort Ward — plus whatever 305 is doing when a boat dumps.

Official civic overview: City of Bainbridge Island. Maps if you want the picture, not the trivia.

Walk-on vs car is the practical version of this answer: getting around.