From Draftsperson.net
Written by Allan
Created 2July2004
Metric ISO Sheets
 The ratio length to width of ISO sheets is 1 : Square Root 2. A square root is a number that when multiplied by itself will produce the given number (the square).
 An A0 sheet is 1m². This allows paper weights to be expressed in grams per square meter. Example: 110gsm paper.
 This relationship of 1: Sq root 2 is particularly important for reduction onto microfilm, or reduction and enlargement on photocopiers. All metric equipment including microfilm cameras, microfilm printers, photocopiers, and even drawing pen sizes, are designed around this ratio. This makes the process of archiving drawings, resizing, and modifying drawings easy.
 Each smaller sheet size is exactly half the area of the previous size. If you cut an A0 sheet in half you get two A1 sheets; If you cut an A1 sheet in half you get two A2 sheets; and so on ...
 The standard widths for rolls is 860 mm and 610 mm.
 ISO is an acronym for International Organization for Standardization
 * Oversize sheets are used when it is desirable to give extra protection to the drawing sheets by providing a binding or trimming margin.
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Cut Sizes of Metric ISO Sheets
Designation 
<b>Width (mm) 
<b>Length (mm) 
A0 
841 
1189 
A1 
594 
841 
A2 
420 
594 
A3 
297 
420 
A4 
210 
297 
A5 
149 
210 
B1 
707 
1000 
B2 
500 
707 
B3 
353 
500 
B4 
250 
253 

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Cut Sizes of Oversized* Metric ISO Sheets
Designation 
<b>Width (mm) 
<b>Length (mm) 
RA0 
860 
1220 
RA1 
610 
860 
RA2 
430 
610 
RA3 
305 
430 
RA4 
215 
305 
RA5 
153 
215 
RB1 
723 
1019 
RB2 
510 
723 
RB3 
361 
510 
RB4 
255 
361 

