03820 -- U.S. ZIP code Municipality (1990): MADBURY, New Hampshire All ZIPs for this municipality (1990): 03820 Population (2000): 28537 Housing Units (2000): 12530 Land area (2000): 39.792023 sq. miles (103.060862 sq. km) Water area (2000): 0.699545 sq. miles (1.811814 sq. km) Total area (2000): 40.491568 sq. miles (104.872676 sq. km) Located within: New Hampshire (NH) Location: 43.190984 N, 70.887878 W