Postcodes in the UK: how they work

A UK postcode is a short series of letters and numbers that identifies a postal address, narrowing it from the area down to the specific street. There are 120 postcode areas in the UK, and Royal Mail maintains the data for over 29 million delivery points.

The history of UK postcodes

The idea of the postcode was first proposed in 1959 to speed up labour-intensive letter sorting. The system was set up in 1965 to reduce an address to a machine-readable code, and after recoding in 1974 the modern postcode era began. Today postcodes are used not just for mail but for insurance, sat-nav and much more.

How postcodes work

Take a postcode like M1 1AE:

• M1 1AE – the first letters show which of the 120 UK postcode areas the address is in.
• M1 1AE – the number narrows it to a district within that area.
• M1 1AE – the final characters identify the specific street or group of addresses.

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Frequently asked questions

How many postcode areas are there in the UK?

There are 120 postcode areas.

When were UK postcodes introduced?

The system was set up in 1965 and completed after recoding in 1974, having first been proposed in 1959.

What does the first part of a postcode mean?

The first letters identify the postcode area; the following number narrows it to a district.