The international phone number format, also known as the E.164 standard, is the globally recognized way to write a phone number so it can be dialed from any country. Using this international phone number format ensures your call or message reaches the correct destination every time, regardless of where you are dialing from.
What is the international phone number format?
The official international standard for phone numbers is E.164, established by the International Telecommunication Union (ITU-T). This format guarantees every telephone number is unique worldwide, supporting efficient routing of calls and messages across global networks. The basic structure is: +[country code][national destination code][subscriber number]. The plus sign (+) is a notation that indicates the number should be dialed with an international calling prefix, which varies by the country from which the call is made.
Components of an E.164 number
An E.164 number is built from three distinct parts. The country code (CC) is 1 to 3 digits long, assigned by the ITU-T, and identifies the nation of the number (e.g., +1 for the United States, +44 for the United Kingdom). The national destination code (often called the area code) routes the call to a specific geographic region within that country. Finally, the subscriber number is the unique local line assigned to an individual or business. Together, these components enable telecommunication networks to direct your call from any origin to the exact endpoint.
How to write a phone number in international format
To write any local number in the correct international format, follow these steps:
- Start with a plus sign (
+). - Add the country code (e.g., 1 for the US, 44 for the UK).
- Remove any trunk code (a leading
0used for domestic dialing). Certain countries use trunk codes or national dialing prefixes for domestic calls. When dialing internationally, it's important to omit these trunk codes and dial the actual country code to ensure that the call is directed to the correct country. Failing to remove trunk codes can result in failed connections or misrouted calls. - Append the remaining local number, including the area code and subscriber number.
For example, a US local number like (212) 555-1234 becomes +1 212 555 1234. A UK local number like 020 7946 0123 becomes +44 20 7946 0123 (the leading 0 is removed).
Dialing international numbers from mobile vs. landline
Mobile phones typically allow direct dialing of numbers including the + sign, as the mobile network automatically inserts the correct international dialing prefix. For landlines, you must manually dial your country's international exit code before the country code. For example, from the US or Canada you dial 011 (the exit code), then the country code and number. From most European countries, you dial 00 as the exit code. Knowing these international calling codes and dialing rules is essential for successfully placing a call from any type of phone. To streamline international communication, consider saving international contacts with their respective country codes in your phone's address book. This practice eliminates the need to manually input country codes each time you make an international call, saving time and reducing the likelihood of dialing errors. Before making frequent international calls, explore international calling plans offered by your phone service provider. These plans often provide discounted rates for international calls, helping you manage communication costs while staying connected across borders.
Key rules and limits for international numbers
E.164 numbers are limited to a maximum of 15 digits and should only contain decimal digits (0-9). Special characters like parentheses, hyphens, or spaces are not part of the standard format. Crucially, you must never include local trunk prefixes (such as a leading 0) when writing or dialing an international number, as this will break the routing.
Frequently Asked Questions
How do I convert my local phone number to international format?
Start with a plus sign, then add your country code. Remove any leading trunk code (like a 0) from the area code or local number, and write the remaining digits without spaces or special characters. For example, a UK number 01632 960 001 becomes +44 1632 960 001.
Can I use the international phone number format for domestic calls?
Yes, you can dial a number in international format even when calling within the same country. Most modern phone systems, especially mobile networks, recognize the + sign and will route the call correctly, though it is not required for domestic calls.
Are there variations in the international phone number format across different countries?
Yes. While the E.164 standard is universal, the length of the country code (1-3 digits), the use and length of area codes, and the format of the local subscriber number all vary by country. Always check the specific numbering plan for your destination country.
What happens if I dial an international number without the plus sign?
If you dial without the +, your phone will treat the number as a domestic call and likely fail or route to an incorrect number. The + tells the network to use the correct international exit code for your location.
Why do some international numbers have more than 15 digits?
They shouldn't. The E.164 standard limits numbers to a maximum of 15 digits total (including the country code). If you encounter a number longer than that, it likely includes extra dialing prefixes or extensions that should be handled separately.
For the wider topic, see international calling codes and dialing.
