What is E.164 international format?
ITU-T E.164 defines the international public telecommunication numbering plan. For a geographic destination, the international number combines the country code with the national significant number. The complete international number is limited to 15 digits. The plus sign and display spaces help people interpret the number, but they are not counted as E.164 digits.
| Part | Purpose | Stored in E.164 digits? |
|---|---|---|
| + | Portable notation for the international prefix | No |
| Country calling code | Routes to a country, shared plan, or global service | Yes |
| National significant number | Identifies the destination inside that numbering plan | Yes |
| Domestic trunk prefix | Domestic routing instruction such as 0 | Usually no; Italy is a notable exception |
| Exit/IDD prefix | Origin-network instruction such as 00, 010, 011, or 0011 | No |
| Extension | Routes after the main destination is reached | No |
What does the plus sign mean in a phone number?
The plus sign means “use the international prefix for the network where this call starts.” ITU-T E.123 uses + to signify that prefix. A US-origin call may replace + with 011, many European networks use 00, Japan commonly uses 010, and Australia uses 0011. Saving + instead of a fixed exit code makes a contact portable between countries and networks.
When should I remove the leading zero?
Remove a leading zero only when the destination country defines it as a domestic trunk prefix. Do not apply that rule globally. The United Kingdom, Germany, France, Japan, Australia, South Africa, and the UAE remove it in the reviewed patterns below; Italian geographic numbers retain their leading zero internationally.
| Country/plan | Domestic pattern | International pattern | Zero rule |
|---|---|---|---|
| United Kingdom | 020 7946 XXXX | +44 20 7946 XXXX | Remove |
| United States | (212) 555-01XX | +1 212 555 01XX | No trunk zero |
| Italy | 06 XXXXXXXX | +39 06 XXXXXXXX | Retain |
| Japan | 03 XXXX XXXX | +81 3 XXXX XXXX | Remove |
| Brazil | 0 XX 11 XXXX XXXX | +55 11 XXXX XXXX | Remove routing prefix/carrier code |
Worked international dialing examples
The X characters are placeholders, not a callable subscriber number. They make the numbering structure concrete without publishing a private number.
United Kingdom landline pattern
Remove the first 0 from 020, then add +44.
- Domestic display
- 020 7946 XXXX
- International display
- +44 20 7946 XXXX
- +44Country code: United Kingdom
- 20Area code: London code without the trunk 0
- 7946 XXXXSubscriber number: Placeholder digits
United States landline pattern
Add +1 before the ten-digit NANP number; do not remove any digit.
- Domestic display
- (212) 555-01XX
- International display
- +1 212 555 01XX
- +1Country code: North American Numbering Plan
- 212Area code: New York example area
- 555 01XXLocal number: Fictional-use pattern
Italy landline pattern
Add +39 and retain the 0 at the start of geographic code 06.
- Domestic display
- 06 XXXXXXXX
- International display
- +39 06 XXXXXXXX
- +39Country code: Italy
- 06Area code: Rome code with its significant leading 0
- XXXXXXXXSubscriber digits: Placeholder digits
Japan landline pattern
Remove the first 0 from 03, then add +81.
- Domestic display
- 03 XXXX XXXX
- International display
- +81 3 XXXX XXXX
- +81Country code: Japan
- 3Area code: Tokyo code without the trunk 0
- XXXX XXXXSubscriber digits: Placeholder digits
Brazil landline pattern
Remove 0 and the two-digit carrier code XX; keep area code 11; add +55.
- Domestic display
- 0 XX 11 XXXX XXXX
- International display
- +55 11 XXXX XXXX
- +55Country code: Brazil
- 11Area code: São Paulo example area
- XXXX XXXXLandline number: Eight-digit placeholder pattern
How should a phone number be stored versus displayed?
Canonical storage
Use a separate field containing + and digits only when your system has confidently parsed a complete number. Store an extension separately.
+442079460123
Human display
Apply country-appropriate spaces for readability. Punctuation is presentation, not proof that the number is valid or reachable.
+44 20 7946 0123
Use the privacy-preserving format checker to inspect punctuation, exit prefixes, extensions, and reviewed leading-zero rules in your browser.
Primary sources
- ITU-T E.164: The international public telecommunication numbering planInternational Telecommunication Union. Verified 2026-07-19.
- ITU-T E.123: Notation for national and international telephone numbersInternational Telecommunication Union. Verified 2026-07-19.
- The National Telephone Numbering PlanOfcom. Verified 2026-07-19.
- National numbering plan: United KingdomInternational Telecommunication Union. Verified 2026-07-19.
- National numbering plan: United StatesInternational Telecommunication Union. Verified 2026-07-19.
- Piano di numerazioneAGCOM. Verified 2026-07-19.
- National numbering plan: ItalyInternational Telecommunication Union. Verified 2026-07-19.
- National numbering plan: JapanInternational Telecommunication Union. Verified 2026-07-19.
- National numbering plan: BrazilInternational Telecommunication Union. Verified 2026-07-19.
See our editorial and sourcing methodology.