Country calling codes, country dial-in codes, international subscriber dialing (ISD) codes, or most commonly, telephone country codes are telephone number prefixes for reaching telephone subscribers in foreign countries or areas via international telecommunication networks. Country codes are defined by the International Telecommunication Union (ITU) in ITU-T standards E.123 and E.164. The prefixes enable international direct dialing (IDD).
Country codes constitute the international telephone numbering plan. They are used only when dialing a telephone number in a country or world region other than the caller's. Country codes are dialed before the national telephone number, but require at least one additional prefix, the international call prefix which is an exit code from the national numbering plan to the international one. In most countries, this prefix is 00, an ITU recommendation; it is 011 in the countries of the North American Numbering Plan while a minority of countries use other prefixes.
Overview
The nine world zones are generally organized geographically, with exceptions for political and historical alignment.
Zone 1 uses an integrated numbering plan; four digits (1xxx) determine the area served in Canada, the United States and its territories, and much of the Caribbean.
Zones 3 and 4 use sixteen 2-digit codes (30–34, 36, 39–41, 43–49) and four sets of 3-digit codes (35x, 37x, 38x, 42x) to serve Europe.
Zone 5 uses eight 2-digit codes (51–58) and two sets of 3-digit codes (50x, 59x) to serve South and Central America.
Zone 6 uses seven 2-digit codes (60–66) and three sets of 3-digit codes (67x–69x) to serve Southeast Asia and Oceania.
Zone 7 uses an integrated numbering plan; two digits (7x) determine the area served: Russia or Kazakhstan.
Zone 8 uses four 2-digit codes (81, 82, 84, 86) and four sets of 3-digit codes (80x, 85x, 87x, 88x) to serve East Asia, South Asia and special services. 83x and 89x are unallocated.
Some of the larger countries were assigned two-digit codes to compensate for their usually longer domestic numbers. Small countries were assigned three-digit codes, which also has been the practice since the 1980s.
41 (91) – Campione d'Italia, an Italian enclave. 91 is actually the prefix for the Swiss canton Ticino in which the enclave resides. Its phone system is fully integrated into the Swiss system.
This table lists in its first column the initial digits of the country code shared by each country in each row, which is arranged in columns for the last digit. When three-digit codes share a common leading pair, the shared prefix is marked by an arrow, ( ↙ ) pointing down and right to the three-digit codes. Unassigned codes are denoted by a dash (—). Countries are identified by ISO 3166-1 alpha-2 country codes; codes for non-geographic services are denoted by two asterisks (**).