E.164 phone number format

E.164 is the international phone number format defined by the ITU: a +, the country code, then the national number without its trunk prefix - at most 15 digits, no spaces, dashes or brackets. +442079460000 is E.164; 020 7946 0000 and +44 (0)20 7946 0000 are not.

Paste a number below to convert it. A number written the local way needs its country.

The E.164 rules

• Starts with +, then the country code: 1 to 3 digits (1 for the US and Canada, 44 for the UK, 353 for Ireland). Country codes never start with 0.
• 15 digits at most, counting the country code and not the +. So a stored E.164 string fits in 16 characters.
• Digits only after the +: no spaces, dashes, dots or brackets.
• No trunk prefix - the 0 (or 8 in Russia) you dial inside the country goes. +44 (0)20... is a display habit, not a valid number.
• No exit code - 00 or 011 is what you dial to leave a country; the + replaces it.
• No extensions - E.164 has no place for ext. 204; keep it in a separate field.

National number to E.164: examples by country

Most countries just drop the leading 0, but not all of them. These are the cases that break naive "strip the zero" code.

E.164 regex - and why it is not enough

The usual pattern checks the shape:

^\+[1-9]\d{1,14}$

It accepts +10000000000 and +999999: right shape, but no country assigns those numbers. A regex cannot know that UK numbers have 10 digits after +44, that US numbers 555-0100 to 555-0199 are reserved for fiction, or that Argentine mobiles need the 9. Use it as a quick filter on input, then validate against the numbering plan - Google's libphonenumber (ports for every major language) or an API.

E.164 vs other formats

• E.164 - +442079460000. For storage, comparison and APIs: one number, one string.
• International (ITU E.123) - +44 20 7946 0000. The same digits with spaces, for people to read.
• National - 020 7946 0000. How the number is dialled inside its country. Ambiguous without the country: 8663982896 is a US number, and other digit strings are valid in several countries at once.

Storing phone numbers in E.164

• Store the E.164 string (varchar(16)) as the canonical value and put a unique index on it - duplicates written as (866) 398-2896 and +1 866-398-2896 collapse into one.
• Convert at input time, while you still know the user's country (from the form, the billing address or the account), not later in a batch job.
• Format for display from E.164, not the other way round.

E.164 for SMS and voice APIs

Twilio, Vonage, Amazon SNS and most other SMS and voice providers expect the destination in E.164. A local-format number is the most common cause of "invalid To number" errors: the provider cannot guess the country. Convert and validate before the send, and drop numbers that do not resolve - a failed send still costs a request, and a landline cannot receive an SMS code.

The DialCode API does that in one call: GET /v1/phone/{number}?country=GB returns the E.164 form, the line type (mobile, landline, VoIP) and scam-risk signals. For a whole list, use the bulk phone number validator.

FAQ