How are telephone area code regions determined?

Answer 1

The USA, Canada and Caribbean nations devolve responsibility for this to an organisation called NANPA.

In the UK, the government body Ofcom carries out the same job.

Other countries will have different setups - normally either a regulator or the main phone company will be involved.

Answer 2

The process of dividing a country into telephone area codes varies significantly from country to country.

In the United States, the area code is always three digits, and the local number is always seven digits. Thus, major metropolitan areas will have multiple area codes, while a few entire states have only one each. In the US, the numbers for the area codes were assigned with the specific intention of not grouping similar numbers together.

Many other countries have area codes of varying lengths, so that a major city has a short area code with longer local numbers, while a small town in a rural area might have a longer area code but shorter local numbers. Some countries assign the area code numbers with a definite geographic pattern. For example, all area codes in the part of Germany that used to be East Germany begin with +49 3 (or 03 in domestic format).

In each case, there is a governmental or quasi-governmental regulatory body that makes the decisions.

Answer 3

In the United States, area codes are assigned by the North American Numbering Plan Administrator in consultation with the state public utilities commission (or equivalent state agency) and local telephone companies. Area codes must start with digits 2 through 9, cannot have 9 as the middle digit (reserved for future expansion to longer phone numbers), and cannot have the second and third digits the same (e.g., 533 or 866; these codes are reserved for non-geographic purposes). To the maximum extent possible, NANPA and the state avoid assigning as an area code a three-digit number that already exists as a prefix in or near the affected area. The state will usually reserve an area code several years in advance so that the corresponding prefix can be marked as unassignable. NANPA also handles assignment of area codes for places outside the US and Canada that are part of telephone country code +1. For example, when the Dominican Republic needed two overlay area codes, NANPA assigned 829 and 849.

In Canada, certain area code numbers have been reserved through NANPA for use in Canada, but the Canadian government makes the final assignment.

In the UK, area code assignments are handled by OFCOM, a governmental agency.

In other countries, area code assignments are generally handled by the government ministry responsible for telecommunications.

Answer 4

US area codes are assigned by the North American Numbering Plan Administrator, in consultation with the state public utilities commission or similar agency.