A UK postcode is a short string of letters and numbers that identifies a small cluster of delivery points — usually up to about 15 addresses. Created by Royal Mail, postcodes make it fast to sort mail and to find a precise address from just a few characters.
What a postcode is used for
- Routing and sorting Royal Mail deliveries
- Address lookup and autocomplete at online checkouts
- Linking locations to delivery zones, pricing and demographics
- Verifying that an address actually exists
A quick example
Take SW1A 1AA. The first part (SW1A) is the outward code identifying the postal district; the second part (1AA) is the inward code narrowing it to a specific group of addresses. Learn more in UK postcode format explained.
Look up any postcode
Want to turn a postcode into a full address in your app? See the Postcode Lookup API or read the full PAF guide.
Frequently asked questions
What is a UK postcode?
A UK postcode is a short combination of letters and numbers (for example SW1A 1AA) that identifies a small cluster of delivery addresses — typically up to around 15 properties.
How many postcodes are there in the UK?
There are roughly 1.8 million live postcodes in the UK, covering around 31 million addresses, all maintained by Royal Mail.
What does a postcode tell you?
A postcode pinpoints a small geographic area, helping route mail, find addresses at checkout, and link locations to data like demographics or delivery zones.
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