Editing Engineering drawing (section)

=== Sizes of drawings ===
{{Main|Paper size}}
[[File:A size illustration.svg|thumb|ISO paper sizes]]
[[File:ANSI_size_illustration.svg|thumb|ANSI paper sizes]]

Sizes of drawings typically comply with either of two different standards, [[ISO standard|ISO]] (World Standard) or [[ANSI/ASME Y14.1]] (American).

The metric drawing sizes correspond to international [[paper size]]s. These developed further refinements in the second half of the twentieth century, when [[photocopying]] became cheap. Engineering drawings could be readily doubled (or halved) in size and put on the next larger (or, respectively, smaller) size of paper with no waste of space. And the metric [[technical pen]]s were chosen in sizes so that one could add detail or drafting changes with a pen width changing by approximately a factor of the [[square root of 2]]. A full set of pens would have the following nib sizes: 0.13, 0.18, 0.25, 0.35, 0.5, 0.7, 1.0, 1.5, and 2.0&nbsp;mm. However, the International Organization for Standardization (ISO) called for four pen widths and set a colour code for each: 0.25 (white), 0.35 (yellow), 0.5 (brown), 0.7 (blue); these nibs produced lines that related to various text character heights and the ISO paper sizes.

All ISO paper sizes have the same aspect ratio, one to the square root of 2, meaning that a document designed for any given size can be enlarged or reduced to any other size and will fit perfectly. Given this ease of changing sizes, it is of course common to copy or print a given document on different sizes of paper, especially within a series, e.g. a drawing on A3 may be enlarged to A2 or reduced to A4.

The US customary "A-size" corresponds to "letter" size, and "B-size" corresponds to "ledger" or "tabloid" size. There were also once British paper sizes, which went by names rather than alphanumeric designations.

[[American Society of Mechanical Engineers]] (ASME) [[ANSI/ASME Y14.1]], Y14.2, Y14.3, and Y14.5 are commonly referenced standards in the US.