The most common entry on my paper list of dialing mishaps is a single digit that should not have been there, or one that should have been. International numbers look like a wall of figures, yet every one of them is built from the same few parts. This page names those parts, one at a time, in plain words. Read it through once, then keep it as a lookup. Terms in italics inside an entry have an entry of their own.
The parts of a number
- Country code
- One to three digits that pick the national phone system you are calling, such as 44 for the United Kingdom or 49 for Germany. The United States and Canada share the code 1 with a number of Caribbean nations, as explained in why numbers start with +1. A full list of zones and common codes sits on the calling codes cheat sheet.
- Exit code
- The digits that tell your own carrier "this call leaves the country". Also called the international call prefix or international access code. It is chosen country by country, which is why it is not the same everywhere. See 011, 00 and the plus sign.
- Area code
- The next piece after the country code: a city or regional code, or a mobile prefix. In the North American plan it is always three digits. In London it is 20. It narrows the call to a region, and it records where a number was first issued, not where its owner stands today.
- Subscriber number
- The last piece, the digits that pick one line inside the area. In the North American plan it is seven digits, split in your head as three and four. Lengths abroad vary a lot, which is one more reason to copy a foreign number exactly as written.
- Trunk prefix
- A digit that a country asks you to dial before the area code on calls inside that country. In the United Kingdom and Germany it is usually 0. It is a domestic habit with no place in an international call, so it disappears when a country code comes first. In the North American plan the nearest relative is the dialed 1, covered below under dialed 1.
- Leading zero
- The trunk prefix as it shows up in a printed number, such as 020 7946 0000. Drop it when you add a country code, so that number becomes +44 20 7946 0000. Keeping it is the most frequent reason a copied foreign number fails. Some countries print it in brackets, as in +44 (0) 20, which is a reminder to leave it out.
- E.164
- The ITU's name for the standard international number: a plus, a country code and the national number, in at most fifteen digits, with no spaces that matter. It is the format a phone sends to the network and the one to save in a contact. The how-to side of it is in saving contacts in international format.
Ways to start the call
- 011
- The exit code of the United States and Canada. From a US landline you dial 011, then the country code, then the area code without its zero, then the line. A call to London reads 011 44 20 7946 0000. It is never part of the number itself, and it means nothing if you dial it from another country.
- 00
- The exit code of much of Europe and of a good number of countries elsewhere. A phone in Germany sends it when you use a plus sign. A few places use something else again, for instance 010 in Japan and 0011 in Australia, and carriers sometimes add their own options. How the exit codes of other countries differ is the subject of a short checklist on dialing out.
- Plus sign
- On a mobile phone, an instruction that means "replace me with the exit code of whatever network I am on". In the US the phone sends 011, in Germany 00. That is why a contact saved with a plus works in every country. On many keypads you touch and hold 0 to type it. Landlines and many office systems do not understand it, so there you dial the exit code yourself. It costs nothing extra: the destination and your plan set the rate, not the way you begin the call.
- Dialed 1
- The trunk prefix of the North American plan, dialed before ten digits when a call leaves your local area. It is not the same as the country code 1, and it does not go in front of 011. When it is required and when it is optional is worked out in when to dial 1 before the area code.
- Mobile prefix
- The area-code position filled by a mobile network instead of a city. UK mobile numbers print as 07..., so from abroad they follow the same rule as landlines: the zero goes, and the number becomes +44 7... Some countries do not use a trunk zero at all, so check how the number is written in international form before you edit it.
- Roaming
- Using your phone on a foreign network. While roaming, the phone registers with the local network and the plus sign is translated for that country. Calls, texts and data can be priced differently under one plan, so ask your carrier about each before you travel.
When a call fails
- Doubled country code
- A number that already starts with its country code and gets a second one added, such as +44 44 20... or +1 1 212.... Copying a number from a website that shows it in international form, then adding your own prefix, is the usual way it happens. Delete the extra one.
- "Not in service" message
- A recording from your own carrier saying the number you dialed is not in service. When it comes at the very start of an international call, it usually points to a format error rather than a dead line. Check the leading zero, the doubled code and whether you added 011 and a plus together.
- International block
- A setting on a line that stops outgoing international calls. Some prepaid and business lines ship with it switched on. If every foreign number fails, even ones that are certainly right, ask the carrier through its official customer service whether international calling is enabled.
- Same-looking numbers
- Codes inside the North American plan that dial like domestic ones but sit in other countries, for example 876 for Jamaica or 242 for the Bahamas. No exit code is needed, so nothing in the dialing hints that the charge may be international. The page on calling Canada and the Caribbean walks through it.
- Unfamiliar foreign prefix
- A country code you do not recognise on a missed call. It is a fact about the number, not a verdict on the caller: plenty are family, couriers and customer-service lines, and some are bait to make you call back. Leave it alone until you know what it means, and check it in the prefix reader if it is a +1 code.
- Worked example
- A friend in Berlin writes that her number is 030 1234 5678. Germany is 49 and Berlin's area code is 30 once the zero is dropped, so you save +49 30 1234 5678. From a mobile you tap the contact and the call goes. From a landline you dial 011 49 30 1234 5678. If her mobile starts 0151, the same rule applies: it becomes +49 151 followed by her digits.
Next in the bookWhy numbers start with +1, and how country calling codes work