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E.164 International Phone Number Format

Updated 2026-10-23 · By the SMS Conecta team (SMSConecta Inc.)

Short answer: E.164 is the ITU-T recommendation laying out the international public telephone numbering plan, including the format for writing any number globally: a plus sign, the country code, then the national number, with no spaces and no leading trunk zero, 15 digits maximum overall. A UK number written as 020 7946 0000, for instance, becomes +442079460000.

Apps, SIP systems and verification services tend to expect E.164 because it pins a number down uniquely no matter where it's being dialled from.

Definition

ITU-T Recommendation E.164 assigns country codes and caps an international number at 15 digits. The plus sign simply stands in for whatever international dialling prefix applies wherever you happen to be.

How it works

National formatE.164
(415) 555-0123 (US)+14155550123
020 7946 0000 (UK)+442079460000
030 123456 (Germany)+4930123456

Formatting rules

  • Lead with + followed by the country code
  • Drop the national trunk prefix, which is usually a leading 0
  • Strip out spaces, dashes and brackets
  • Keep the whole thing to 15 digits or fewer

How it applies to SMS Conecta

Whether dialling from the web dialer, a SIP app, or entering a SMS Conecta number into an app for verification, use the full international form. The country code tool and phone number formatter can convert a local format for you.

Related terms

  • DID
  • Mobile number
  • Caller ID

Frequently asked questions

Does the plus sign count as part of E.164?

The standard itself is just the digits; the plus is a conventional marker of an international number that most apps expect to see.

Why does an app keep rejecting my number?

Double-check you've picked the right country and haven't left in the national leading 0.

What is the maximum length of an E.164 number?

Up to 15 digits total, country code included.

Why does a US number start with 1?

Because +1 is the shared country code for the US, Canada and other NANP countries.

Related pages

Get a number in these countries

Sources