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Europe · +44

United Kingdom phone number format

  • Country code +44
  • Trunk prefix 0

Reviewed by Sujan ThapaliyaLast updated

What does a United Kingdom phone number look like?

10 digits after the trunk 0 (9 for a few older area codes). Landlines are written +44 20 XXXX XXXX and mobiles +44 7XXX XXXXXX. In full international (E.164) format a United Kingdom mobile is written +447700900123: the country code +44, with the national trunk prefix 0 removed, and no spaces or punctuation.
The anatomy of a United Kingdom phone number under ITU-T E.164: country calling code 44, then the national destination code, then the subscriber number, to a maximum of fifteen digits after the plus. Nationally a United Kingdom number is written +44 20 XXXX XXXX with the trunk prefix 0; in E.164 the prefix and the spacing both come off.
National formatting is for people. E.164 is for databases, APIs, and caller ID — store United Kingdom numbers in the right-hand form.

Format rules

Country code
+44
National number length
10 digits after the trunk 0 (9 for a few older area codes)
Trunk prefix
0
Used only domestically. Removed in international format.
Landline pattern
+44 20 XXXX XXXX
Mobile pattern
+44 7XXX XXXXXX

Examples

United Kingdom phone number examples

Ofcom reserves 020 7946 0XXX and 07700 900XXX for drama and documentation, so these examples cannot ring a real person.

TypeWritten domesticallyInternational (E.164)
Landline020 7946 0123+442079460123
Mobile07XXX XXXXXX+447700900123

A quirk of United Kingdom numbering

The leading 0 in 020 or 07911 is a domestic trunk prefix. Drop it when dialling from abroad: +44 20…, never +44 020…

Validation

How to validate a United Kingdom number

Validating a phone number is three separate checks, and conflating them is the usual source of bugs:

  1. Format: does it match the shape for United Kingdom? 10 digits after the trunk 0 (9 for a few older area codes), after the country code and with the 0 stripped.
  2. Allocation: is the prefix actually in use? A number can be the right length and still belong to an unallocated range.
  3. Reachability: is there a live subscriber? Only a carrier lookup (HLR or equivalent) answers that, and it is the only check that catches disconnected numbers.

For form validation, check format only and be permissive: accept spaces, dashes, brackets, and a leading 0 then normalise. Rejecting a real customer because they typed their own number the way they normally write it is a far more expensive error than storing one badly formatted row.

Store in E.164 (+447700900123) and format for display at render time. Storing the display format is how a database ends up with the same person recorded four different ways.

Format any number instantly

Paste a number into the free phone number formatter to convert it to E.164 and see whether it matches United Kingdom’s format rules. No sign-up.

Frequently asked questions

What does a United Kingdom phone number look like?
10 digits after the trunk 0 (9 for a few older area codes). A landline is written +44 20 XXXX XXXX and a mobile +44 7XXX XXXXXX. In full international format that becomes +447700900123.
How do I write a United Kingdom number in international format?
Start with +44, remove the leading 0 from the national number, then append the rest with no spaces or punctuation. +44 20 7946 0123 becomes +442079460123.
How many digits is a United Kingdom phone number?
10 digits after the trunk 0 (9 for a few older area codes).
How do I tell a United Kingdom mobile from a landline?
By the prefix. Mobiles follow the pattern +44 7XXX XXXXXX, while landlines follow +44 20 XXXX XXXX.
Should I store phone numbers with the plus sign?
Yes. Store every number in E.164: leading +, country code, national number, no spaces or punctuation, up to 15 digits. It is the only format that is unambiguous internationally, and it is what makes deduplication work. Format for display, store canonical.

Sources

  1. ITU-T Recommendation E.164 — The international public telecommunication numbering plan — International Telecommunication UnionThe international number format, the 15-digit maximum, and how country codes and national numbers compose.
  2. ITU-T International Numbering Resources — International Telecommunication UnionThe assignment of country calling codes and the published national numbering plans they belong to.

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