bay covers somewhere between 400 and(-) 1600 sqmi, depending on which sub-bays (such as San Pablo Bay), estuaries, wetlands, and so on are included in the measurement. The main part of the bay measures 3 to(-) 12 mi wide east-to-west and somewhere between 48 mi¹ and 60 mi² north-to-south.

San Francisco Bay is the second-largest estuary on the Pacific coast of the Americas, following the Salish Sea in Washington State and British Columbia, Canada.