The System International (SI) specifies an A-size series of drawing sheets for engineering drawings. Figure 1.2 shows the basic A0 sheet that has an area of one square meter.

Figure 1.2

The size of an A0-size

Other A-size drawing sheets are the Al, A2, A3, A4 and A5. All A-size sheets have their edge lengths in the same proportion. This proportion is in the ratio of the short side to the long side and is written as 1:

Each lower-size sheet in the A series is obtained by exactly dividing the A sheet along its centre. This results in a wide range of sizes with a size to suit every purpose. This is shown in Figure 1.2

Figure 1.3 shows the relationship between the various sizes of the A-series drawing sheets. There are A-size drawing sheets that are larger than the ones already mentioned, for example 2A0 and 4A0. There are smaller sizes too, for example, A6 and A7. In schools and colleges, and during the examination of drawing, the size sheets most commonly used are A2, A3 and A4.

Remember that the drawing sheets are rectangular and not square.

Reference to Table 1.2 shows that:

• the Al size is half of the area of the A0 size
• the A2 size is half of the area of the A1 size
• the A3 size is half of the area of the A2 size
• the A4 size is half of the area of the A3 size.

Figure 1.3

The relationships of the A-size series sheets

Table 1.2

Dimensions of drawing sheets

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