Agree with styx71. A lot of the blocks in Armadale are still larger blocks with some having been subdivided. The new suburbs like Haynes and Hilbert the blocks are a lot smaller between 300m2 and 500m2...the average being 360m2.
Armadale has a good range of blocks with the smallest being either new or subdivided ones - about 350 land area would be the minimum. The average would be 750 m2 and some development blocks may be from 1000-2000m in the older areas, but these are now becoming less common as the area gets developed.