What is the E.164 Format, and how to use it correctly

The E.164 format is the name of the code that specifies the format, structure, and administrative hierarchy of telephone numbers. It is an international standard called “The International Public Telecommunication Numbering Plan” and defines a numbering plan for the global public switched telephone network. 

In short, the E.164 format is a general format for international telephone numbers.

What is the E.164 format?

E.164 is a standard format for international telephone numbers recommended by the International Telecommunication Union. This format ensures that each PSTN (Public Switched Telephone Network) device has a distinct and unique number worldwide.

A globally unique telephone number will ensure that calls and SMS can be routed correctly to different individual phones worldwide.

Structure and examples

The E.164 format requires the following:

• A + sign. This sign may be optionally used when presenting numbers in E.164 format (*1).
• Country calling code (international).
• Local area code.

Local telephone number or subscriber number.

It has the following structure: [+][country code][area code][subscriber number].

Example of a number with E.164 format in the United States

Telephone number: 415 123 1234
E.164 format number: +14151231234

• Country code: +1
• Area code: 415
• Subscriber number: 1231234

Example of an E.164 format number in the United Kingdom

Telephone number: 07851 987654
E.164 format number: +1447851987654

• Country code: +44
• Area code: 7851
• Subscriber number: 987654

Example of an E.164 format number in Spain

Telephone number: 632 123 456
E.164 format number: +34632123456

• Country code: +34
• Area code: 632
• Subscriber number: 123456

How to dial an E.164 phone number correctly

The E.164 format has certain peculiarities. To dial a phone number correctly and ensure delivery of calls and SMS, you should remember the following:

• When entering the complete number, there should be no spaces between the elements (+ sign, country code, area code, and subscriber number).
• Telephone numbers in E.164 format are limited to 15 digits.
• Some telephone numbers, such as Scottish numbers, start with 0. If this is the case, you should remove the 0, as this prefix is only used for national calls. If you call from a foreign country, it will give an error.

Using this format is the best way to guarantee the success of your calls and SMS.

In VoIPstudio, you can find a list of calling codes by country and access to national or international geographic numbers in more than 30.000 cities.

If you have questions about the E.164 format and how to use it from VoIPstudio, do not hesitate to contact our technical support team.

(*1) Note: As explained before + sign may be optionally used when presenting numbers in E164 format, however it is not part of the standard RFC 2806.

Prefixing the E164 number with the sign “+” is meant to indicate to the reader that the digits are a phone number in E164 format, and it’s called “globalized format of an E.164 number”.