The purpose of this site is to explain current international standard paper sizes, covered by the ISO 216 Standard, and to provide size charts to allow a quick lookup of sizes.
If you are looking for the specific size of a particular paper format these are available on the following pages:
ISO Paper Sizes Standard Overview & Rationale:
The ISO paper size A standard is based on each size being half of the size of the previous one when folded parallel to the shorter lengths. This system allows for a variety of useful applications, such as the enlarging and reducing of images without any cutoff or margins, or folding to make a booklet of the next size down.
The mathematics behind this useful feature is that the sheets have an aspect ratio (that's the ratio of the length to the width) of the square root of 2.A Series Paper Sizes Formal Definition
The ISO 216 definition of the A paper sizes are based on the following basis:
Sizes for A Series Paper - A0, A1, A2, A3, A4, A5, A6, A7 and A8
Extensions - B Series Paper Sizes: There are some requirements for paper sizes where the A series isn't suitable and to take these into account the B series paper sizes were introduced. In order to explain the rationale behind the B paper sizes, we are going to need a bit more maths.
The B series paper standards are also based around the 1: root 2 aspect ratio, but in order to provide sizes not covered by the A series, the length and width of size B(n) are defined as being the geometric mean of size A(n) and size A(n-1).
Note: The geometric mean of two numbers is the square root of the product of those two numbers. e.g. The geometric mean of 6 and 4 is root(6x4) or the square root of 24. (For those who are interested - this link explains Geometric Means in more detail.)
The benefit of using the geometric mean is that the magnification factor between A1 and B1 sizes is that same as the one that scales B1 to A0.
Sizes for B Series Paper - B0, B1, B2, B3, B4, B5, B6, B7, and B8
The C Series Envelope Sizes: The C series sizes were introduced to define the sizes of envelopes suitable for the A series paper sizes. This is also based on the root 2 aspect ratio and the size of a C(n) envelope is defined as the geometric mean of paper sizes A(n) and B(n). This leads to a C(n) envelope which nicely holds a sheet of A(n) paper unfolded.
This sizing also has some neat properties when dealing with folded paper so a C4 envelope will hold a sheet of A4 paper unfolded, a C5 envelope will hold a sheet of A4 paper folded in half once parallel to its shortest sides and a C6 envelope will hold the same piece of paper folded twice.
Sizes for C Series Envelopes - C0, C1, C2, C3, C4, C5, C6, C7 and C8
If you are looking for the specific size of a particular paper format these are available on the following pages:
ISO Paper Sizes Standard Overview & Rationale:
The ISO paper size A standard is based on each size being half of the size of the previous one when folded parallel to the shorter lengths. This system allows for a variety of useful applications, such as the enlarging and reducing of images without any cutoff or margins, or folding to make a booklet of the next size down.
The mathematics behind this useful feature is that the sheets have an aspect ratio (that's the ratio of the length to the width) of the square root of 2.A Series Paper Sizes Formal Definition
The ISO 216 definition of the A paper sizes are based on the following basis:
- The length divided by the width is 1.4142
- The A0 size has an area of 1 square meter.
- Each subsequent size A(n) is defined as A(n-1) cut in half parallel to its shorter sides.
- The standard length and width of each size are rounded to the nearest millimeter.
Sizes for A Series Paper - A0, A1, A2, A3, A4, A5, A6, A7 and A8
Extensions - B Series Paper Sizes: There are some requirements for paper sizes where the A series isn't suitable and to take these into account the B series paper sizes were introduced. In order to explain the rationale behind the B paper sizes, we are going to need a bit more maths.
The B series paper standards are also based around the 1: root 2 aspect ratio, but in order to provide sizes not covered by the A series, the length and width of size B(n) are defined as being the geometric mean of size A(n) and size A(n-1).
Note: The geometric mean of two numbers is the square root of the product of those two numbers. e.g. The geometric mean of 6 and 4 is root(6x4) or the square root of 24. (For those who are interested - this link explains Geometric Means in more detail.)
The benefit of using the geometric mean is that the magnification factor between A1 and B1 sizes is that same as the one that scales B1 to A0.
Sizes for B Series Paper - B0, B1, B2, B3, B4, B5, B6, B7, and B8
The C Series Envelope Sizes: The C series sizes were introduced to define the sizes of envelopes suitable for the A series paper sizes. This is also based on the root 2 aspect ratio and the size of a C(n) envelope is defined as the geometric mean of paper sizes A(n) and B(n). This leads to a C(n) envelope which nicely holds a sheet of A(n) paper unfolded.
This sizing also has some neat properties when dealing with folded paper so a C4 envelope will hold a sheet of A4 paper unfolded, a C5 envelope will hold a sheet of A4 paper folded in half once parallel to its shortest sides and a C6 envelope will hold the same piece of paper folded twice.
Sizes for C Series Envelopes - C0, C1, C2, C3, C4, C5, C6, C7 and C8
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