What is E.164 phone number format?
Posted: Tue May 27, 2025 8:11 am
The E.164 phone number format is an international numbering standard established by the International Telecommunication Union (ITU). It defines the structure and format for telephone numbers to ensure consistency and interoperability across global telecommunication networks. The E.164 standard is critical for enabling calls and messages to be routed correctly anywhere in the world.
Key Features of E.164 Format
International Standard: E.164 is the most widely adopted format for representing phone numbers internationally.
Max Length: It allows phone numbers up to a maximum of 15 digits.
Only Digits: The format consists only of digits (0-9), with no spaces, dashes, or other separators.
Starts with Country Code: The number always begins with the country calling code, allowing automatic recognition of the country or territory.
Structure of an E.164 Number
An E.164 number is composed of three main parts:
Country Code (CC):
This is a numeric code assigned to each country or region, ranging from 1 to 3 digits.
For example, the United States and Canada share recent mobile phone number data the country code “1,” while the UK uses “44” and India uses “91.”
National Destination Code (NDC) or Area Code:
This identifies a specific geographic area, city, or mobile network operator within the country.
Its length varies by country.
Subscriber Number (SN):
This is the unique number assigned to an individual subscriber or line.
The total length of the country code plus national number should not exceed 15 digits.
Example of an E.164 Number
For example, a US phone number formatted in E.164 would look like:
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+14155552671
“+1” is the country code for the USA.
“415” is the area code for San Francisco.
“5552671” is the subscriber number.
Similarly, a UK number in E.164 would be:
diff
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Edit
+442079460958
“+44” is the UK country code.
“20” is the London area code.
“79460958” is the subscriber number.
Why Use E.164?
Universal Compatibility:
Since E.164 is a global standard, phone numbers formatted this way can be recognized and dialed from anywhere in the world without ambiguity.
Avoids Formatting Conflicts:
Local dialing conventions, such as using a trunk prefix (“0”) in many countries, are excluded in E.164. This ensures a clean, unambiguous number for international routing.
Enables Automated Systems:
Telecom switches, VoIP systems, and mobile networks rely on E.164 for routing calls efficiently and accurately.
Facilitates Number Validation:
Applications that need to validate or store phone numbers use E.164 as the canonical format to avoid inconsistencies.
How to Write an E.164 Number?
Begin with a “+” sign (or sometimes the international dialing prefix like “00” is used, but “+” is preferred in writing).
Follow with the country code.
Append the national number without trunk prefixes or separators.
Do not include spaces, parentheses, or hyphens.
For example, a French number might be:
diff
Copy
Edit
+33123456789
(not: 01 23 45 67 89 or 0033 1 23 45 67 89)
E.164 and Modern Technologies
Mobile Apps & APIs: Many services (like WhatsApp, Twilio, Firebase Authentication) require phone numbers in E.164 format for verification and communication.
International Calling: Networks use E.164 to route calls correctly.
Number Portability: Helps systems track and route numbers even when moved between operators.
Conclusion
The E.164 phone number format is a crucial global standard for representing phone numbers in a uniform, internationally understood way. By using a simple, digit-only format starting with a country code and allowing up to 15 digits, E.164 ensures seamless communication across countries and networks. For developers, telecom operators, and businesses alike, adopting E.164 format is essential for ensuring accurate dialing, validation, and user convenience in global communications.
Key Features of E.164 Format
International Standard: E.164 is the most widely adopted format for representing phone numbers internationally.
Max Length: It allows phone numbers up to a maximum of 15 digits.
Only Digits: The format consists only of digits (0-9), with no spaces, dashes, or other separators.
Starts with Country Code: The number always begins with the country calling code, allowing automatic recognition of the country or territory.
Structure of an E.164 Number
An E.164 number is composed of three main parts:
Country Code (CC):
This is a numeric code assigned to each country or region, ranging from 1 to 3 digits.
For example, the United States and Canada share recent mobile phone number data the country code “1,” while the UK uses “44” and India uses “91.”
National Destination Code (NDC) or Area Code:
This identifies a specific geographic area, city, or mobile network operator within the country.
Its length varies by country.
Subscriber Number (SN):
This is the unique number assigned to an individual subscriber or line.
The total length of the country code plus national number should not exceed 15 digits.
Example of an E.164 Number
For example, a US phone number formatted in E.164 would look like:
diff
Copy
Edit
+14155552671
“+1” is the country code for the USA.
“415” is the area code for San Francisco.
“5552671” is the subscriber number.
Similarly, a UK number in E.164 would be:
diff
Copy
Edit
+442079460958
“+44” is the UK country code.
“20” is the London area code.
“79460958” is the subscriber number.
Why Use E.164?
Universal Compatibility:
Since E.164 is a global standard, phone numbers formatted this way can be recognized and dialed from anywhere in the world without ambiguity.
Avoids Formatting Conflicts:
Local dialing conventions, such as using a trunk prefix (“0”) in many countries, are excluded in E.164. This ensures a clean, unambiguous number for international routing.
Enables Automated Systems:
Telecom switches, VoIP systems, and mobile networks rely on E.164 for routing calls efficiently and accurately.
Facilitates Number Validation:
Applications that need to validate or store phone numbers use E.164 as the canonical format to avoid inconsistencies.
How to Write an E.164 Number?
Begin with a “+” sign (or sometimes the international dialing prefix like “00” is used, but “+” is preferred in writing).
Follow with the country code.
Append the national number without trunk prefixes or separators.
Do not include spaces, parentheses, or hyphens.
For example, a French number might be:
diff
Copy
Edit
+33123456789
(not: 01 23 45 67 89 or 0033 1 23 45 67 89)
E.164 and Modern Technologies
Mobile Apps & APIs: Many services (like WhatsApp, Twilio, Firebase Authentication) require phone numbers in E.164 format for verification and communication.
International Calling: Networks use E.164 to route calls correctly.
Number Portability: Helps systems track and route numbers even when moved between operators.
Conclusion
The E.164 phone number format is a crucial global standard for representing phone numbers in a uniform, internationally understood way. By using a simple, digit-only format starting with a country code and allowing up to 15 digits, E.164 ensures seamless communication across countries and networks. For developers, telecom operators, and businesses alike, adopting E.164 format is essential for ensuring accurate dialing, validation, and user convenience in global communications.