Blueprint Reading

6 Chapter 1

ISO Standards.

The metric drawing sizes correspond to international paper sizes, in Europe and many other countries
ISO (International Standards Organization) metric measurements are used (Table 1.1). The ISO defines
a set of standard metric line widths for drafting. For example, the ISO A series of sheet sizes is based
on a constant width to length ratio of 1: 2. Thus, each smaller sheet size is exactly half the area of the
previous size, so that if we cut an A0 sheet in half, we get two A1 sheets; if we cut an A1 sheet in half,
we get two A2 sheets; and so on. In Figure 1.2 the A0 size is defined as having an area of 1 square me-
ter. This lets us express paper weights in grams per square meter.
The relationship of 1: 2 is particularly important for reduction onto microfilm or reduction and en-
largement on photocopiers. Metric equipment including microfilm cameras, microfilm printers, photo-
copiers, as well as drawing pen sizes are designed around this ratio. This simplifies the process of
archiving drawings, resizing, and modifying drawings.
Like the ISO A-series sheet sizes, the pen sizes increase by a factor of two, which allows additions
and corrections to be made on enlargements or reductions of drawings. Each width is assigned a color
code. The color code corresponds to that for the matching lettering stencil. Line widths and color codes
are standardized across all manufacturers.

Other Standard-Setting Organizations.

As previously mentioned, ANSI and ISO are the two main drafting-standard-setting bodies. However,
there are other organizations that have developed engineering standards that complement these. Like

U.S. ENGINEERING DIMENSIONS (inches) DIMENSIONS (mm)

ANSI A 8.5 11 215.9 279.4

ANSI B 11 17 279.4 431.8

ANSI C 17 22 431.8 558.8

ANSI D 22 34 558.8 863.6

ANSI E 34 44 863.6 1117.6

U.S. ARCHITECTURAL DIMENSIONS (inches) DIMENSIONS (mm)

ARCH A 9 12 228.6 304.8

ARCH B 12 18 304.8 457.2

ARCH C 18 24 457.2 609.6

ARCH D 24 36 609.6 914.4

ARCH E 36 48 914.4 1219.2

MISCELLANEOUS DIMENSIONS (inches) DIMENSIONS (mm)

LETTER 8.5 11 215.9  279.4

LEGAL 8.5 14 215.9 355.6

U.S. GOVERNMENT 8 11 203.2 279.4

STATEMENT 5 8.5 139.7 215.9

Table 1.1 ANSI (American National Standards Institute) standard recommended sheet sizes.