North American Numbering Plan

The North American Numbering Plan (NANP) governs the managment of telephone numbers for the Public Switched Telephone Networks in North America (Canada, USA, Carribean, and territories) within the international country code prefix '+1'.

North American phone numbers are in the format (where N is any digit from 2-9, and X from 0-9):



NPA identifies the 3-digit Numbering Plan Area (Area Code)
NXX identifies the Central Office (aka. Exchange) within the NPA
XXXX identifies the Station within the NXX

In NPAs that do not require overlay facilities numbers of the form NXX-XXXX are colloquially refered to as local and numbers of the form 1-NPA-NXX-XXXX are known as long distance. In certain NPAs, particularly large urban areas, the maximum number of available NXX and Station code combinations has been reached, requiring additional non-toll NPA's to be assigned - these are known as overlay facilites and their presence is generally reflected by 'local' numbers taking on the form NPA-NXX-XXXX and 'long distance' the form 1-NPA-NXX-XXXX. The NANPA maintains historical assignments statistics on Station and Exchange code use within each NPA and periodically issues exhaustion projections (eg. which are used to advertise and plan network structure changes.

Unlike many countries calls between the majority of local stations in the United States and Canada are toll-free, with only long distance calls incuring a toll charge. The requirement for prefixing a leading 1 to place a toll call is known as requiring toll alerting. The need for toll alerting varies from NPA to NPA however it is universally active in Canada and implemented for many other jurisdictions in the NANP.

The official managment website for the NANP is


The North American numbering plan is available in a data base called the LERG maintained by Telcordia.
The LERG has data for every switch and central office in the North American telephone network.
Copies of the LERG can be purchased from Telcordia. LERG info is constantly changing, so most users subscribe to periodic updates.

Subsets of the information in the LERG are available free on the Web:

A user submitted VBScript is available to quickly export the Excel data to a MySQL script. View


Maps are available that show Central Office locations, local calling areas, and other information

Mapquest will generate a map show the approximate Central Office location if you invoke it with a URL like this:
change the areacode and exchange values to match the NPA-NXX you want to display.

Other Map sources:

Local Calling Area


Special Use NPA

Potentially Premium Rate NPAs

  • 900-NXX-XXXX--premium rate numbers, prices vary
  • 700-NXX-XXXX--defined by long distance carrier, one generally calls 1-700-555-4141 toll-free to identify the carrier
  • 500-NXX-XXXX--personal communication services (follow me)
  • 533-NXX-XXXX--was reserved for expansion of personal communication services, but the reservation has been withdrawn

Potentially Premium Rate Exchanges

  • NPA-976-XXXX

Toll-Free Special Use NPAs

  • 800-NXX-XXXX
  • 888-NXX-XXXX
  • 877-NXX-XXXX
  • 866-NXX-XXXX
  • 855-NXX-XXXX

Carrier Identification Codes

Also known as CIC codes, PIC codes, Dial-Around Numbers, 1010 Numbers, 101XXXX Codes, etc.

See Also

Created by: jht2, Last modification: Sun 20 of Feb, 2011 (08:29 UTC) by admin
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