How Australian Postcodes Work

The 4-digit format

All Australian postcodes are exactly 4 digits long — for example, 2000 (Sydney CBD) or 3000(Melbourne CBD). The system was introduced in 1967 by the then-Postmaster-General's Department to speed up mail sorting, at a time when the volume of letters was growing rapidly and manual sorting by town name alone was becoming impractical.

First digit = state or territory

The first digit of an Australian postcode identifies the state or territory. This makes it easy to determine the general location of any postcode at a glance:

Browse all postcodes by range: 0xxx, 1xxx, 2xxx, 3xxx, 4xxx, 5xxx, 6xxx, 7xxx, 8xxx, 9xxx

Delivery vs. mail centre postcodes

Standard postcodes (starting with 2, 3, 4, 5, 6, 7) are used for street addresses — residential homes, businesses, and institutions. Mail centre postcodes (starting with 1, 8, 9) are reserved for PO Boxes and bulk mail facilities. If you're filling in a form with a home address, you'll always use a standard delivery postcode.

One postcode, multiple suburbs

A single postcode can cover multiple suburbs. For example, postcode 2000 covers both Sydney CBD and Haymarket. Conversely, some large suburbs are split across multiple postcodes — especially in outer metropolitan areas. This is why you should always look up the specific suburb name, not just assume a postcode.

How postcodes are assigned

Postcodes are assigned by Australia Post and follow geographic and delivery route logic — nearby areas generally have similar numbers. Within a state, lower-numbered postcodes tend to be closer to the capital city. For example, in NSW, the 2000s cover inner Sydney, while the 2800–2999 range covers rural and regional areas. New postcodes are occasionally created when large new suburbs are established.