Standard Paper Australian Sizes

Following are the common paper size dimensions in Australia.

Paper Size

A1

A2

A3

A4

A5

A6

A7

A8

Height x Width (mm)

841 x 594 mm

594 x 420 mm

420 x 297 mm

297 x 210 mm

210 x 148 mm

148 x 105 mm

105 x 74 mm

74 x 52 mm

In this list, A1 is the largest size and A8 is the smallest. An easy way to estimate the sizes is that every preceding size is double the size of the following one. For example, A3 is double the size of A4.
In the following pictures, A4 (yellow) can be observed as half the size of A3 (white)

A4 sheet on top of A3
A4 sheet side-by-side of A3

                                                                    

Another interesting thing to note is the width of each size becomes the height of the following size, e.g width of A2 (420mm) is the length of height of A3 (420mm). Another way to look at it is in the image below: