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What is a Postcode Sector?

by Louisa Bainbridge on Nov 9, 2017

What is the definition of a postcode sector?

A postcode sector combines a postcode area, a postcode district and a single character indicating the location's inward code. For example 'SW1A 0' is a sector which is made up of 'SW' which indicates South West London. This area has 139 sectors in it so the district, once focused into 'SW1A' there are only 3 sectors in this area and these are marked with an inward code to narrow this down even further to a more specific geographical area. These are marked numerically, with the district including three sectors numbered 0, 1 & 2. 

Whilst it varies across the UK, there are about 3000 addresses within each sector. There can be up to 10 different sectors within a postcode district and these are numbered 0-9.  The sector information is used by the Royal Mail to define the local area delivery office that the post should be distributed to. 

Postcode sector list providers

Here are a few sources where you can download a list of every postcode sector

Postcode sector map providers

Here are a few sources where you can download or purchase a map or check out our postcode mapping guide here.


The break down of a UK postcode

All UK postcodes are made up of a range of different letters and numbers and follow this format: A postcode area, district, sector, unit.  

Learn more about postcodes at our postcode map and list resource centre


Learn more about postcode maps and tools
Postcode data