City of Tustin City Seal Location of Tustin within Orange County, California. Area[4] • Total 11.082 sq mi (28.701 km2) • Land 11.082 sq mi (28.701 km2) • Water 0 sq mi (0 km2) 0% Elevation[1] 138 ft (42 m) Population (April 1, 2010)[5] • Total 75,540 • Estimate (2013)[5] 78,327 • Density 6,800/sq mi (2,600/km2) Time zone Pacific (UTC−8) • Summer (DST) PDT (UTC−7) ZIP codes 92780–92782 Area code(s) 657/714, 949 FIPS code 06-80854 GNIS feature IDs 1661590, 2412117 Website www.tustinca.org https://en.wikipedia.org/wiki/Tustin,_California