Complete Guide to Postcode Areas in the United Kingdom
This comprehensive guide covers all postcode areas used by Royal Mail for directing mail within the United Kingdom. The postcode area represents the largest geographical unit in the UK postal system and forms the initial characters of alphanumeric UK postcodes.
Overview of UK Postcode Areas
The United Kingdom currently has 121 geographic postcode areas in active use, with an additional three covering the Crown Dependencies of Guernsey (GY), Jersey (JE), and the Isle of Man (IM). These areas were originally introduced between 1959 and 1974 as part of a major modernization of the postal system, replacing the previous postal district system that had been in place since the Victorian era.
Historical Development
The UK postcode system was developed to automate mail sorting following the Second World War. The first postcode area introduced was Norwich (NR) in 1959, with the system being rolled out across the country throughout the 1960s and early 1970s. London was particularly challenging to organize, resulting in its division into multiple postcode areas (E, EC, N, NW, SE, SW, W, WC) rather than the single area originally proposed.
Structure and Format
Each UK postcode follows this format: [Area][District] [Sector][Unit]. For example, in the postcode "SW1A 1AA":
- SW is the postcode area (South West London)
- 1A is the postcode district
- 1 is the postcode sector
- AA is the postcode unit
Geographical Coverage
Postcode areas vary dramatically in size and population coverage. The largest by geographical area is HS (Outer Hebrides), covering approximately 3,071 square kilometers, while the smallest is WC (West Central London) at just 2.5 square kilometers. The most densely populated is EC (East Central London), serving the City of London financial district.
| Postcode Area | Coverage | Notable Locations | Introduced |
|---|---|---|---|
| AB | Aberdeen | Aberdeen, Elgin, Peterhead | 1963 |
| BT | Belfast | All of Northern Ireland | 1974 |
| CF | Cardiff | Cardiff, Newport, Pontypridd | 1966 |
| EH | Edinburgh | Edinburgh, Livingston, Dunfermline | 1965 |
| G | Glasgow | Glasgow, Paisley, Dumbarton | 1964 |
| L | Liverpool | Liverpool, Southport, Ormskirk | 1966 |
| M | Manchester | Manchester, Salford, Stockport | 1965 |
Special Cases and Exceptions
Several postcode areas have unique characteristics:
- BT covers all of Northern Ireland despite its Belfast designation
- GY (Guernsey), JE (Jersey), and IM (Isle of Man) serve Crown Dependencies
- BF was used for British Forces post offices until 2012
- London's unique division into 8 postcode areas rather than one
- ZD, ZE, and ZF are reserved for special purposes
Postcode Area Subdivision
Each postcode area is further divided into:
- Post towns: The main delivery location (e.g., "Cambridge" in CB postcode area)
- Postcode districts: The outward code (first part of postcode)
- Postcode sectors: The first digit after the space
- Postcode units: The final two letters
The number of districts per area varies significantly. The ZE (Shetland Islands) area has just 3 districts, while BT (Northern Ireland) has 81. On average, each postcode area contains about 20 districts.
Geographical Scope and Boundaries
Postcode areas don't align with political or administrative boundaries. They were designed for postal efficiency rather than geographical representation. Some notable examples:
- The PA (Paisley) area stretches from Greenock to Campbeltown, covering 5 local authority areas
- DL (Darlington) serves parts of County Durham, North Yorkshire and Cumbria
- London's 8 postcode areas cover only about 40% of Greater London's total area
Mnemonic Lettering System
The letters chosen for postcode areas were intended to be memorable:
- Single letters for major cities (B=Birmingham, G=Glasgow, L=Liverpool)
- Two letters where single letters were exhausted (AB=Aberdeen, BT=Belfast)
- Some reflect historical county names (HR=Hereford, DT=Dorchester)
- Others use prominent local features (LD=Llandrindod Wells, NP=Newport)
Modern Usage and Applications
Beyond mail delivery, postcode areas are now used for:
- Insurance and financial services rating
- Demographic analysis and marketing
- Emergency service planning
- Academic research and polling
- Online shopping delivery calculations
Future Developments
The Royal Mail periodically reviews postcode areas to accommodate:
- Population growth in expanding cities
- New housing developments
- Changes in mail volume patterns
- Technological advancements in sorting
Interesting Facts
- The shortest postcode is "G1" in Glasgow
- The highest numbered district is "IV63" in the Inverness area
- Some postcode areas cross national boundaries (TD covers England and Scotland)
- The "SAN TA1" postcode was created for Father Christmas's mail