Area Codes and Numbering

The North American Numbering Plan (NANP) is the telephone numbering system within which the Public Switched Telephone Network is managed in the United States, Canada, and some Caribbean countries by the North American Numbering Plan Administrator (NANPA). The NANP is divided into smaller Numbering Plan Areas that are each identified by a three-digit code, commonly known as an area code. Telephone numbers in the NANP are structured in the format NPA-NXX-XXXX, in which

 
NPA is the 3-digit area code that identifies a specific geographic area;

 
NXX is the 3-digit prefix that identifies a specific central office within an area code; and

 
XXXX is the 4-digit line number that identifies a specific line within a central office.

 
The Federal Communications Commission (FCC) has exclusive jurisdiction over telephone numbering in the United States but has delegated specific authority to state regulatory agencies. Tasked with the authority granted by the FCC, the CPUC conducts area code relief and enforces number conservation in California in accordance with Public Utilities Code Section 7930-7943.

California currently has 36 area codes. A new area code is added to a geographic area when there are no more three-digit prefixes available in the existing area code.  Area codes are added in the form of a geographic split or an overlay. California has added twelve area codes using the overlay method since 2006.

California Area Codes

 *overlay

Information for Carriers

• Interconnected voice over internet providers obtaining numbering resources in California must collect and remit surcharges in support of California universal service programs
• Process for carriers requesting safety valve relief