Interesting facts and information about postcodes
Updated 15 Jul 2020
A postcode is not unique to a street. A postcode is made up of components that represent an outward code, inward code, postcode area, district code, sub-district code, postcode sector and postcode unit. The postcode unit is what represents a street, part of a street, a single address or property.
Sometimes a postcode can cover more than one street. For example, the postcode HD7 5UZ covers 7 streets.
Read our postcode format guide for a more comprehensive outline of UK postcode patterns.
The biggest postcode area is IV, also known as Inverness. It is made up of 52 postcode districts for post towns.
There are 124 postcode areas in the United Kingdom. The average size os an area is 776 square miles and the average population is 533,000.
The UK postcode consists of five to seven alphanumeric characters which define four different levels of geographic unit. CH5 3QW has the longest addresses in terms of numbers of elements.
Each postcode area is divided into a number of districts which are represented by the numerical portion of each part of the postcode. These numbers range from 0 to 99.
Including the postcode in a letter is essential to ensure it is delivered to the correct address. However, it may not be enough to put it on its own. A full address should include a premise identifier, street details and post town too.
Read our good addressing guide to ensure your mail is correctly addressed.
Postcodes are updated daily through Royal Mail’s Postcode Address File.
Royal Mail does not make changes to postcodes unless it is absolutely necessary and there is an operational reason. Residents can request changes; however, there has to be enough evidence that all the affected are in favour.
You can find out more in Royal Mail’s Code of Practice
There are 1.7 million postcodes in the UK.
Each postcode covers an average of about 15 properties. However, this is not a definitive number, where postcodes can hold up to 100.