UK numbering for landline numbers and UK mobile numbers follow the E.164 set of standards set out by the ITU-T. This set of standards sets out the international telephone numbering plan that ensures each device on the PSTN is identified by a globally unique number. An international E.164 number is designed to include all of the necessary information to enable successful routing of a call or an SMS message to an individual subscriber on a specific nation’s public switched telephone network. This applies to UK phone numbers and the UK dialling codes or area codes.
How does the E.164 numbering plan work for UK dialling codes?
- A telephone number can only have a maximum of 15 digits
- The first part of the telephone number identifies the country code (one to three digits)
- The second part is the national destination code (NDC)
- Finally comes the part know the subscriber number (SN)
- The NDC and SN together are collectively called the national (significant) number
A UK mobile number example would look like:
- Country code: +44
- National destination code: 7975
- Subscriber number: 777666
- In total: +447975777666
Telephone numbers in the UK have changed substantially over recent years in order to make available more numbers to accommodate a wider range of telephone services, such as VOIP, SIP Trunks, data only SIMS and more. These ongoing changes have resulted in much confusion around showing a UK telephone number. This is evident when looking at the numerous ways landline numbers or UK mobile phone numbers from the same part of the country are displayed. We see it in shops, vehicles, web sites business cards, etc.
So let’s explore not only how the UK phone number format appears, and how it should be shown and also why.
Makeup of a UK telephone number
Putting aside international dialling for now, UK phone numbers are made up 2 parts. Namely these are the local phone number and the area dialling code. The dialling code is what someone in a different area must dial before dialling the number. You can find any UK dialling code check here.
The local phone number is the 5 to 8 digits to be dialled after the area code. Almost all UK phone numbers, including the dialling code, are 11 digits long. There are about 40 area codes with 10 digits. Examples are given below.
So UK area codes can be 3 digits with 8-digit local phone numbers, e.g 020 numbers for London, 4 digits with 7-digit phone numbers or 5 digits with 6-digit or, as mentioned above, sometimes 5-digit phone numbers. Examples of each are given below.
It is helpful to show the area code followed by a space followed by the remaining part of the number separated with a space for easy reading e.g 01332 412251, or 01423 396979. It can sometimes help to add a separator within the local part of the number eg 01332 412 251.
And if doing business outside the UK then it is a good idea to spell it out in an international format for your customers. The leading zero from the area code is dropped, and the number would now be displayed, including the country code, as +44 1332 412251
Since 2001 almost all UK geographic numbers and non-geographic numbers have 9 or 10 significant numbers after the leading “0”. Significant numbers being made up of the national destination code (NDC) and then the subscriber number (SN) as outlined by E.164. UK mobile telephone numbers always have 10 significant numbers after the leading “0” .
3 Digit Codes
3-digit codes all start with 02, followed by a further 8 digit phone numbers, and serve larger metropolitan area populations. All 02 numbers should be shown as 02x xxxx xxxx
The current UK dialling codes in use at present are:
020 London numbers
023 Southhampton & Portsmouth
028 Northern Ireland
The telephone area code number for most of Greater London and some surrounding areas is 020, not “0207”, “0208” or “0203”. ‘020 4’ was introduced in 2019.
020 area code numbers should be displayed in the format 020 yyyy yyyy or (020) xxxx xxxx and for international callers, use: +44 20 yyyy yyyy. Note the leading zero is dropped.
4 Digit Codes
4-digit codes, starting with either 011x or 01×1 and followed by a further 7-digit phone numbers serve large cities and surrounding areas. These normally shown as 01xx yyy yyyy.
There are 12 such are or dialling codes in the UK:
4 Digit UK phone numbers should be shown in the format 01xx yyy yyyy and for international calling +44 1xx yyy yyyy. Note the leading zero is dropped for international callers.Contact Us
5 Digit Codes
5 Digit Codes are used for the remaining codes and begin with 01 and are 5 digits long, then followed by a 5 or 6-digit phone number. Most UK landline numbers are a total of 11 digits, however some locations still have a mixture 10 digits and 11. Matlock 01629 has several 10 digit numbers, as does Buxton 01298. Over 580 areas now use this format.
01283 Burton upon Trent
A full list of all UK dialling codes can be found here
5 Digit UK phone numbers should be shown in the format 01xxx yyyyyy and for international calling +44 1xxx yyyyyy. Note the leading zero is dropped for international callers.
If you do need to have non-UK customers call you, then you will need to show the number in the international format.
In the UK and most of Europe, the international dialling code is 00. However, it is not the same throughout the world so the normal convention is to use + as a placeholder for the international dialling code, leaving the caller to insert their code as appropriate.
The country code for the UK is 44. It is also not necessary to dial the leading zero when calling into the UK from outside the country, so this is shown in a bracket. For example, +44 (0) 1423 396979 for Harrogate 01423 396979.
To dial out to other countries you will first dial the International Direct Dialing (IDD) number. The UK uses 00, other countries have different numbers, or may have more than one IDD.
Then you will need the Country Code, usually unique for each country although the US, Canada and the Caribbean share the same one! An excellent site to find the international country dialling code you need is here.
Finally you need the local phone number. So dialling someone in the US on 213 4560789, then you would dial 00 the IDD number, then the Country code for USA which is 1, followed by the full area code and local number, so 00 1 213 4560789 in this case. Don’t forget if you are calling from a PBX office phone system, you may need to dial a 9 to get outside dial tone!Contact Us
101 is a Non-emergency number for the Police only. 101 is only available if you are calling from within England, Wales, Scotland or Northern Ireland.
111 is a relatively new telephone service to contact the NHS. It is the number you should call when one requires advice or medical treatment quickly, but you cannot wait for an appointment to see your own doctor.
112 was introduced in 1995 in the UK. It was introduced across Europe in order to give a consistent and standard number for anyone travelling within the EU. Calls route to exactly the same services as 999 and works in exactly the same way. The important thing about 112 is that it will work from a mobile phone anywhere in the world.
119 UK network operators have been asked to create a new national dialling code namely 119. It is be used as a part of the NHS COVID-19 response. It will help to handle COVID-19 specific cases which in turn will take pressure off the 111 NHS Direct service.