Tonawanda is located at 43°1'13" North, 78°52'49" West (43.020278, -78.880278).
According to the United States Census Bureau, the city has a total area of 18.93 mi2 (49.02 km2). 17.37 mi2 (44.98 km2) of it is land and 1.56 mi2 (4.04 km2) of it is covered by water. The total area is 8.24% water.
Tonawanda is located in the Eastern Standard Time (EST) timezone, GMT-05:00. It observes Daylight Saving Time (DST).