Image: Ilya Akinshinxxxx on Adobe Stock

To find the paper sizes for A, B, and C sheets of the ISO standard, read on!

What is ISO Paper anyway?

ISO (International Organisation for Standardisation) 216 paper sizes are based on an aspect ratio of approximately 1:1.4142 – the square root of 2. The base format (A0) is a sheet spanning 1m² in area. Successive sheets in the series are made by halving the preceding paper size along the larger edge.

The advantage of this system lies in scaling: if a sheet with an aspect ratio of √2 is divided into two equal halves parallel to its shortest sides, then the halves will again have an aspect ratio of √2.

Developed from earlier ideas in Germany in 1922, the system quickly spread to other countries, and was established as an ISO standard in 1975.

A Series

The most frequently used of this series is A4. The US ‘Letter’ paper size – that you may frequently select by mistake in MS Word (as I do) – is 6mm wider and 18mm shorter than this.

SheetDimensions (mm)
A01189 x 841
A1841 x 594
A2594 x 420
A3420 x 297
A4297 x 210
A5210 x 148
A6148 x 105
A7105 x 74
A874 x 52
A952 x 37
A1037 x 26

B Series

In less common use, the B Series is the geometric mean of successive A sheets. B sizes are usually found in poster design, books and envelopes.

SheetDimensions (mm)
B01414 x 1000
B11000 x 707
B2707 x 500
B3500 x 353
B4353 x 250
B5250 x 176
B6176 x 125
B7125 x 88
B888 x 62
B962 x 44
B1044 x 31

C Series

The C series is used only for envelopes. The area of C series sheets is the geometric mean of the areas of the A and B series sheets of the same number.

SheetDimensions (mm)
C01297 x 917
C1917 x 648
C2648 x 458
C3458 x 324
C4324 x 229
C5229 x 162
C6162 x 114
C7114 x 81
C881 x 57
C957 x 40
C1040 x 28