The Official National Zone Charts identify the appropriate distance code assigned to each originating and destinating ZIP Code™ pairing for every ZIP Code in the nation. These distance codes, referred to as "zones", are designated as "Local" and "1 through 8". Zone charts create a matrix of originating and destinating ZIP Codes and identify the correct zone for the distance.

Zone charts are produced by the U.S. Postal Service using geological survey files of established latitude and longitude coordinates to determine the distance between originating and destinating ZIP Code pairings. The files include all ZIP Codes listed in the City State Product.

Order forms are available for mailers who want to purchase a complete set of Official National Zone Charts, which are available on electronic media and/or hard copy from the National Customer Support Center. There is also a zone chart lookup for any individual 3-digit ZIP.

For more information, please call the National Customer Support Center at 1-800-238-3150.