Telephone numbering plan

A telephone numbering plan is a type of numbering scheme used in telecommunication to assign telephone numbers to subscriber telephones or other telephony endpoints. Telephone numbers are the addresses of participants in a telephone network, reachable by a system of destination code routing. Telephone numbering plans are defined in each of administrative regions of the public switched telephone network (PSTN) and they are also present in private telephone networks.

Numbering plans may follow a variety of design strategies which have often arisen from the historical evolution of individual telephone networks and local requirements. A broad division is commonly recognized, distinguishing open numbering plans and closed numbering plans. A closed numbering plan imposes a fixed number of digits to every telephone number, while an open numbering plan allows variance in the numbers of digits. Many numbering plans subdivide their territory of service into geographic regions designated by an area code, which is a fixed-length or variable-length set of digits forming the most-significant part of the dialing sequence to reach a telephone subscriber.

Telephone numbers in the Americas

Canada, the United States and some Caribbean countries use the country calling code 1. Local area codes in these countries are managed by the North American Numbering Plan.

Greenland and Aruba have a country calling code that has the number "2" as first digit, which mostly is used by countries in Africa. All other countries use codes that start with "5".

North American Numbering Plan

Country Code: +1
International Call Prefix: 011
Trunk Prefix: 1

In the United States (including its territories), Canada, Bermuda, and 18 Caribbean nations, area codes are regulated by the North American Numbering Plan. Currently, all area codes (officially called numbering plan areas) in the NANP must have 3 digits. Historically, the second digit was always "0" or "1", while the second digit of the 3-digit exchange prefix was never "0" or "1." With the increased demand for area codes because of additional lines, FAX lines, pagers, cell phones, etc., the restrictions on the second digit were lifted in 1995. At the same time, the historic restriction on a local (7-digit) telephone number's second digit, which previously could not be a "0" or "1" (to avoid confusion with area codes), was also lifted. Under the new rules, a telephone number such as (378) 400-1234 is perfectly legal, whereas before 1995 it was not permitted.

Telephone numbers in Asia

States and territories with country calling codes

States and territories without a separate country calling code

See also