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3. The ISO paper series

The ISO paper format consists of five main series ; “A”, “B”, “C”, “RA” and “SRA”.

“A”……….. The “A” series is defined as having a parent size of 841 x 1189 mm and an area of one square metre rounded up. This gives us the paper weight in grams per square metre written as gsm and stated as its grammage.

Cutting this sheet in half gives us 2 x A1 sheets. Cutting the A1 sheet in half again gives us 2 x A2 sheets , cutting an A2 sheet in half once again gave us 2 x A3 sheets and so on.

Each halving of the sheet gives us the next smaller A sized format and this is illustrated in Fig # 2. The measurements have been rounded up to the nearest mm.

Table # 3 The ISO sizes

*Format*	*Common Uses*	*Size in mm*
AO	Posters, Technical Drawings	841 x 1189
A1	Posters, Technical Drawings	594 x 841
A2	Posters, Wall charts Technical Drawings	420 x 594
A3	Posters, Wall charts Technical Drawings	297 x 420
A4	Letters, catalogs,magazines,documents	210 x 297
A5	Note-pad, Books, Menu cards	148 x 210
A6	Postcards, Timetables	105 x 148
A7	Phamplets	74 x 105
A8	Credit cards, Playing cards	52 x 74

“B”………… The “B”series was intended as an intermediate range format whereby the 100% increase in area when moving up from an A4 to an A3 format was not required or may have been too drastic. The “B” series provided an intermediate alternative and the move from an A4 format to a B4 format only increased the page area by about 41.5% and not 100%.

This format is centered on a parent sheet size of 1000 x 1414 mm and is not commonly used in the printing industry . The format sizes are listed in table #4.

Table # 4 The “B” series

*Format*	*Size in mm*
B0	1000 x 1414
B1	707 x 1000
B2	500 x 707
B3	353 x 500
B4	250 x 353
B5	176 x 250
B6	125 x 176
B7	88 x 125
B8	62 x 88

“C”………. The “C” series format is mainly used for folders and envelopes to hold the corresponding members “A” sized products either flat or folded.

A C4 envelope is designed to hold an A4 sized document, a C5 envelope can either hold a flat A5 sheet or an A4 sheet folded in half as shown in Fig # 3. The “C” series format sizes are tabulated in Table #5.

The DL sized envelope is not really a part of the ISO series but is quite common in business use and is designed to hold an A4 sized letter folded twice.

Its size is normally 110 x 220 mm but some companies do use a 114 x 229 mm format as these are claimed to be much easier to process on automatic inserting and enveloping machines.

Table # 5 tabulates the standard “C” series

Table # 5 The “C” series

Format	Size in mm
C0	917 x 1296
C1	648 x 917
C2	458 x 648
C3	324 x 458
C4	229 x 324
C5	162 x 229
C6	114 x 162
C7	81 x 114
C8	57 x 81

“RA” and “SRA”….. The “RA” and “SRA” series are mainly for printers and are slightly larger than the corresponding “A” size in order to accommodate trim margins, bleeds and colour bars.

The “RA” series is approximately 5% larger than the corresponding “A” size and may only have space for the inclusion of trim margins and bleeds while the “SRA” series is larger by about 15%.

The “SRA” series normally allows stripping in of full sized colour bars for quality control purposes in addition to the bleeds and trim margins.

The differences between the “A” series and the “RA” and “SRA” series are indicated in Table # 6.

Table #6 – Comparison of A, RA and SRA series in mm

Format size	A series	RA series	SRA series
O	841 x 1189	860 x 1220	900 x 1280
1	594 x 841	610 x 860	640 x 900
2	420 x 594	430 x 610	450 x 640
3	297 x 420	305 x 430	320 x 450
4	210 x 297	215 x 305	225 x 320
5	148 x 210	152 x 215	160 x 225
6	105 x 148	107 x 152	112 x 160
7	74 x 105	76 x 107	80 x 112
8	52 x 74	53 x 76	56 x 80