Two different systems
ZIP Codes are used to help route mail. Telephone area codes are part of the North American Numbering Plan and help route telephone calls. They were created for different infrastructure and purposes.
Different geographic coverage
A ZIP Code may cover part of a city or a delivery area, while an area code can cover a much larger region and may overlap with other area codes through overlays. Neither system is a direct substitute for the other.
Why a location can have several
A city can contain many ZIP Codes and may be served by multiple telephone area codes. Conversely, an area code can span many towns, cities and ZIP Code areas.
Use the right reference
Use ZIP Code data for postal research and telephone numbering resources for phone number questions. Treat any cross-reference as approximate unless supported by a specific authoritative dataset.