Paper sizes and dimensions refer to the physical size and measurements of a sheet of paper. They are standardized by organizations such as ISO (International Organization for Standardization) and ANSI (American National Standards Institute) to ensure consistent and uniform sizes for different types of paper, such as letter, legal, and A4. The dimensions are usually specified in millimeters or inches, and include the length and width of the paper. The most commonly used paper sizes are Letter (8.5 x 11 inches), A4 (210 x 297 mm), and Legal (8.5 x 14 inches).
The A series of paper is the most commonly used worldwide, with only the US and Canada (some parts of Mexico) not currently conforming to the ISO 216 (international standard).
Paper sizes are standardized formats that are used for writing, printing and design. They are defined by the International Organization for Standardization (ISO) and are based on the metric system. The most commonly used paper sizes are:
- A3: 297 x 420 mm (11.69 x 16.54 inches)
- A4: 210 x 297 mm (8.27 x 11.69 inches)
- A5: 148 x 210 mm (5.83 x 8.27 inches)
- A6: 105 x 148 mm (4.13 x 5.83 inches)
These are the most commonly used paper sizes, there are other formats as well like:
- C series, D series, E series, F series, G series, etc.

- The A3 paper size is 297 mm x 420 mm or 11.7 x 16.5 in. A3 in pixels?
- The A4 paper size is 210 mm x 297 mm or 8.3 x 11.7 in. A4 in pixels?
- The A5 paper size is 148 mm x 210 mm or 5.8 x 8.3 in. A5 in pixels?
All paper sizes in millimeters and inches

Read more about the different A papers:
- Size of A0
- Size of A1
- Size of A2
- Size of A3
- Size of A4 (the most common paper size)
- Size of A5
- Size of A6
- Size of A7
- Size of A8
- Size of A9
- Size of A10
About the ISO standard
The International Organization for Standardization (ISO) first published its international standard for paper sizes in 1975, although the format itself is based on the German DIN 476 standard that was first introduced in 1922. The ISO standard for paper sizes is known as ISO 216 and it defines a series of paper sizes based on a single aspect ratio of the square root of two (1:√2). This aspect ratio means that the ratio of the length to the width of each paper size is the same, and each size is simply half the area of the next larger size.
Other paper sizes
Click if you are looking for measurements and information about B size papers or paper sizes in the US standards (used in Canada and Mexico also).