Statistical Area Level 1 (SA1)
The smallest area the ABS uses to publish most Census data. An SA1 is a neighbourhood block of about 400 people, usually between 200 and 800, and SA1s fit together to form SA2s.
What an SA1 is
SA1s are designed to give as much geographic detail as possible while keeping individual answers private. Most have between 200 and 800 residents, about 400 on average, which in a city might be a few streets. Mesh blocks are smaller still, but the ABS only releases population and dwelling counts for them.
There are 63,485 SA1s in the 2026 boundaries, up from 61,845 in 2021, mostly from growth on the edges of cities. Each is built from whole mesh blocks, and whole SA1s make up each SA2. Some SA1s are deliberately empty, covering parks, industrial land or water, and the ABS calls these zero SA1s.
Codes, not names
SA1s don't have names. Each has an 11-digit code made up of the code of the SA2 it sits in plus two digits of its own. That makes them easy to join to other data and awkward to talk about, so it helps to describe one by the suburb or SA2 it's in.
When SA1s help
- Building custom areas. Because they're small, SA1s are the best pieces for assembling a catchment, trade area or sales territory that doesn't follow standard boundaries.
- Seeing inside a larger area. A suburb or SA2 can hide very different streets. Its SA1s show where the pockets are.
- SEIFA. The ABS builds its SEIFA indexes from SA1s, so this is the finest level SEIFA scores come at.
Things to watch
- Small numbers are noisy. The ABS makes small random changes to every Census figure to protect privacy. In an area of 400 people that can move a percentage noticeably, so compare groups of SA1s rather than reading one on its own.
- Detail runs thin. Breakdowns such as income by age leave very few people in each group at this level, too few to read reliably.
- They change. SA1s are redrawn more often than larger areas, especially where populations are growing, so comparing one SA1 across Censuses needs care.
SA1s in Censible
Censible builds the catchments you draw, and the areas around your sites, from 2026 SA1s, weighting each by how much of it falls inside. You can also search an SA1 by its code: it appears as a neighbourhood block of about 400 people, with the SA2 it sits in named underneath.
Source: ABS, Australian Statistical Geography Standard (ASGS) Edition 4, Statistical Area Level 1.
Statistical Area Level 2 (SA2)
A medium-sized area defined by the ABS to represent a community that interacts socially and economically. Most have between 3,000 and 25,000 residents.
Socio-Economic Indexes for Areas (SEIFA)
SEIFA is a set of four ABS indexes that rank areas of Australia by relative socio-economic advantage and disadvantage, using Census data. Each area gets a score, a rank and a decile, where decile 1 is the lowest-scoring 10% of areas and decile 10 the highest.
Suburbs and Localities (SAL)
The ABS's approximation of officially recognised suburbs and localities, built from mesh blocks. It replaced State Suburbs (SSC) from the 2021 Census.
Mesh block
The smallest area in the ABS's boundaries, designed where possible to hold 30 to 60 dwellings and tagged with a broad land use. The ABS releases only population and dwelling counts for mesh blocks, and builds every larger area, including councils, suburbs and postcodes, from them.
Area weighting (apportioning)
A way to estimate figures for an area that doesn't match published boundaries, by giving it a share of each overlapping area's counts. The share can follow land area, population or dwellings, and each assumes the figure is spread evenly within what it measures.
Perturbation (small-cell adjustment)
The small random adjustments the ABS makes to Census counts so that no individual can be identified. The ABS calls it introduced random error. It barely affects large counts, though it can distort very small ones, and it means table totals may not equal the sum of their parts.
Questions people ask
The ABS's smallest area for publishing most Census data: a neighbourhood block of about 400 people. SA1s fit together to form SA2s.
Most have between 200 and 800 residents, with about 400 on average. Some, called zero SA1s, cover parks, industrial land or water and have no residents at all.
There are 63,485 in the 2026 boundaries, up from 61,845 in 2021.
There are too many of them for names to be practical, so the ABS identifies each with an 11-digit code. The first nine digits are the code of the SA2 it belongs to.