E.164 number formatter

What E.164 is

E.164 is the ITU standard for international phone numbers. A number in E.164 is a +, a country code of one to three digits, and the national significant number, with no spaces, brackets, leading zeros or extensions. The whole thing is never longer than 15 digits. +442079460018 is E.164. 020 7946 0018, +44 (0)20 7946 0018 and 0044 20 7946 0018 are the same number written for people.

Switches, SIP trunks and dialers want one predictable format, because they make routing decisions by matching the leading digits. A stray trunk prefix or a missing country code sends the call to the wrong rate deck entry, or to no route at all. On a CLI route, a malformed caller ID is one of the most common reasons a call is rejected or shown as unknown.

What the formatter fixes

• Punctuation. Spaces, dashes, dots and brackets are removed.
• Exit codes. 00 and the North American 011 are read as the international prefix and replaced by +.
• Trunk prefixes. The national 0 (or 1 in North America) is removed. The (0) that people write after +44 or +49 is removed too, because it is never dialled from abroad.
• Missing country codes. Numbers without a country code take the default country you choose.
• Country quirks. Italian fixed numbers keep their 0. Argentine mobiles get the 9 after +54 and lose the domestic 15. Brazilian carrier selection codes and the retired Mexican 044, 045 and 01 prefixes are removed.
• Extensions. Text such as ext 204 or x204 is dropped, since extensions are dialled after the call connects.

E.164 versus trunk format

Most wholesale SIP trunks, including ours, expect the destination and the caller ID as country code plus number with no + and no 00. That is E.164 without the plus sign. The formatter gives you both. Use E.164 for storage and CRMs, and the trunk format in your dialplan or carrier prefix settings.

How the number type is worked out

In most countries the first digits after the country code tell you whether a number is mobile, fixed, toll-free or premium rate. UK mobiles start with 7, French mobiles with 6 or 7, German mobiles with 15, 16 or 17. The formatter checks those ranges and the allowed length for each type.

A "Check" result means the number does not fit the plan: usually a digit too many or too few, or a range that is not issued. It is worth cleaning these out of a dialer list before a campaign. Invalid numbers lower your answer rate and drag down NER, which some carriers read as poor traffic. See ASR, ACD, PDD and NER explained.

Limits of this tool

The tool covers the 20 countries we see most often in call-center traffic and uses simplified ranges. It checks format, not whether a number is live. Everything runs in your browser and no numbers are sent to us. For lists in other countries, or for millions of rows, normalise in your CRM with a library such as libphonenumber.