Tumwater is located at 47°0'25" North, 122°54'29" West (47.007222, -122.908056).
According to the United States Census Bureau, the city has a total area of 10.08 mi2 (26.11 km2). 9.95 mi2 (25.77 km2) of it is land and 0.13 mi2 (0.34 km2) of it is covered by water. The total area is 1.30% water.
Tumwater is located in the Pacific Standard Time (PST) timezone, GMT-08:00. It observes Daylight Saving Time (DST).