Oakley is located at 37°59'51" North, 121°42'39" West (37.997500, -121.711111).
According to the United States Census Bureau, the city has a total area of 12.52 mi2 (32.42 km2). 12.42 mi2 (32.16 km2) of it is land and 0.10 mi2 (0.26 km2) of it is covered by water. The total area is 0.81% water.
Oakley is located in the Pacific Standard Time (PST) timezone, GMT-08:00. It observes Daylight Saving Time (DST).