How Big Is a Postcode Area?

There is no standard size for a postcode area. In one country, a code might cover a few dozen properties on one side of a street. In another, it might cover a whole town. Even within one country, size changes a great deal between city centres and the countryside.

What decides the size

The area is shaped by delivery needs, not by geography alone:

• the number of addresses in the area
• the amount of mail they receive
• how long it takes a carrier to cover them
• the way the operator's sorting centres are organised

Dense areas are split into many small zones. Sparse areas are grouped into few large ones. See how postcodes are assigned.

Different systems, different granularity

Countries with letter-and-number codes can often narrow down to a small group of addresses. Countries using a short numeric code may have fewer, larger zones. Extended codes subdivide further; see ZIP+4 and extended postal codes.

Shape and boundaries

Postcode areas are drawn around delivery points and routes. They may have odd shapes, follow roads rather than rivers, or be interleaved with others. A street might be split between two codes, with odd numbers in one and even in another. This is why postcode boundaries rarely match administrative ones, and why using them for tax or eligibility needs care; see postcodes and tax calculation.

Why size matters

A larger area means less precision. If you plan to rely on the code for distance estimates, service coverage or risk, remember that two properties with the same code may be far apart. The effects on rural users are covered in postcodes in rural and remote areas.

Compared with a map grid

A grid code has a fixed size by design. UPCS, for example, uses 3 m by 3 m cells, so every code covers the same tiny area wherever it is. That makes it a poor substitute for a postcode in mail sorting, but a good complement when a precise point is needed. Learn more in exact-location codes and postcodes together.