List of UK dialling codes covering Wales

This is a list of geographic UK dialling codes covering Wales that are currently in use. Some exchanges cover both sides of the Wales-England border. All geographic telephone numbers in Wales are in the format (01xxx) xxxxxx, with the exception of Cardiff and the surrounding area which has been (029) xxxx xxxx since the "Big Number Change" in 2000.

(Source: "The Phone Book - Code Companion", BT)

Misconceptions
It is a common misconception that the code for Cardiff is 02920, whereas in fact it is 029 followed by an eight-digit local number. This is due to Cardiff previously having a longer code (0222 then 01222) with six-digit local numbers. From 2000, all of its local numbers (until 2005) had the additional 20 added to them, making them 8 digits long. This problem is also widespread in cities with other 02x codes such as Coventry, London, Portsmouth and Southampton, and in the region of Northern Ireland.