A4 Paper Size

What is A4 Paper Size?


A4 size is one of the paper sizes in the ISO A series. Its specific dimensions are 8.27″ x 11.69″ in inches, 210 x 297 in mm, or 21.0 x 29.7 in cm.

The size of the A paper series was defined by ISO216, which was first put forward by German scientist Georg Christoph Lichtenberg as DIN476 standard of Germany and later adopted by ISO. Under the same standard, there is also B size series, which follows the same rule as A series: ratio of length to width of a piece of paper should be √2:1.

A4 paper can be folded twice to fit fully into a C6 envelope.


As in the scope of ISO paper sizes, A4 paper size is used in most countries and regions in the world, except North American countries, Mexico, Philippines, and other countries affected by American colonization. In these areas, US paper sizes are the most widely used, which belong to a different system.

World Regional Distribution of ISO Paper Sizes and American Paper Sizes
The areas in yellow are where A4 paper size is applied


Like its North American alternative, the letter size, A4 size is the most common paper size in office use, business documents, laws and regulations, government reports, leaflets, restaurant menus and other uses.


The figure below shows A4 dimensions in inches and mm.
A4 paper size in cm is 21.0 x 29.7, this figure is obtained by dividing its dimensions in mm by 10.

A4 Paper Size
A4 Paper Size in inches and mm

A4 Size Table

A4 Dimension in inches, mm, and cm

Size # in inches in mm in cm
A4 8.27″ x 11.69″ 210 x 297 21.0 x 29.7

A4 Dimensions in Pixels

A4 dimensions vary in pixels, depending on the PPI/DPI applied.

Size # 72 dpi/ppi
(screen resolution)
96 dpi/ppi
(screen resolution)
300 dpi/ppi
(print resolution)
A4 595 x 842 px 794 x 1123 px 2481 x 3507 px

* PPI (pixels per inch) = DPI (dots per inch) = Resolution

A Series Size Relations

How did the A4 paper size come about?

The dimension aspect ratio of an ISO216 paper is √2:1, the A series paper size start from the first size, the A0 size.

Cut a A0 sized paper symmetrically at the midpoint of its long edge, you will get two A1 papers; then cut the papers you got in the same way, you will get 4 pieces of A2 sheets, and then 8 pieces of A3 sheets, and then 16 pieces of A4 sheet in the fourth cutting.

A4 and Other Sizes in A series

Based on this scale, each size from A0 to A1A2A3A4A5A6A7A8, A9, A10, etc, is twice the size of the next code. Thus, each A4 sheet is twice the size of A5 sheets, and half the size of an A3 sheet.

The figure below reflects the relationship between the dimensions of ISO paper size A, as well as the relationship between A4 size, letter size (8.5″ x 11″, wider and shorter) and legal size (8.5″ x 14″, wider and longer).

A Paper Sizes Chart
A Paper Sizes Chart in mm

A4 Size vs. Letter Paper Size: Similar in Size but Different

The most of common A size corresponds to a similar size in North American countries, Mexico, the Philippines, and other countries affected by American colonization, for example, A3 size versus ANSI B(tabloid or Ledger), and A4 versus Letter Size. Some imprecise bloggers or website writers even confuse A4 with Letter Paper size.

Just as A3 size can occasionally replace 11×17 paper size, A4 can also be used as a alternative for Letter size in some cases. But they are defined by different systems and used in different regions. Although they are similar in size, they are not the same thing.


  – A4 Paper Size8.27″ x 11.69″
Used in non-North American countries, belongs to ISO A paper sizes

  – Letter Paper Size8.50″ x 11.00″
Specifically called ANSI A paper size, or American Quarto, used in North America, Mexico, the Philippines, etc, is part of the ANSI paper standard of US paper sizes

A4 Paper Size vs. Letter Paper Size
A4 Paper Size vs. Letter Paper Size

The Most Popular Paper Size in the World and Why

In non-American standard countries where ISO standard paper sizes are applicable, there are also many kinds of paper sizes to choose from. For example, only Series A has sizes from A0 to A10 or even A12; The B series has sizes with the same principle. However, A4 is chosen as the most commonly used paper for two reasons.

A4 Paper Consumption
A4 consumption scene in an ordinary office

The most cost-effective size

At the same price, A4 paper is the paper with largest size that you can buy, on which can print the most words and consume less for the same article, so in essence A4 paper is the most cost-effective for printing and copying.

For example, A5 size paper is only half of A4’s, but in some countries the copying price is higher than half of A4’s; A3 size paper is twice as expensive as A4, but the copying price is high than double of A4’s, so actually A4 is currently a dessert price charged for copying.

Therefore, A4 size naturally becomes the most widely used size in the world.

The ergonomic size

From the practical point of view, the size of A4 (8.27″ x 11.69″ in inches, 210 x 297 in mm, or 21.0 x 29.7 in cm) is just one of the most suitable dimensions for ergonomic comfort angle, whether it is used for writing or carrying.

Of course, there must be a size range that is most suitable for ergonomics, and fortunately A4 is exactly in this range and right the size specified by international standards. It should be noted that in North American countries, Mexico, the Philippines and other former colonial areas of the United States, people use letter paper size more as the office size, which measures 8.5″ x 11″ and is very close to A4, is just in this size range too.

In addition, from the perspective of dialectics, the more popular A4 is, the more corresponding manufacturers there are; and the mature technology and intensified competition make its production cost and selling price reach the most reasonable level, thus A4 becoming the best choice for people’s daily use.

The Size of Most Consumed Paper on The Planet and How

A4 Paper consumption: a shocking astronomical figure

Compared with any other size of paper in the world, the A4 size is the most widely used. Most countries and regions in the world use A4 paper as the main consumed paper. It also means that the world consume hundreds of thousands of tons of A4 paper every day, which is a shocking astronomical figure.

Paper consumption and deforestation

A research published in the journal Nature in September 2015 proposed the answer of how many trees are cut down for paper products every year: 15.3 billion trees. By the time this page is being updated by me today in 2021, perhaps that number had increased a lot. What is certain is that among them, a considerable part comes from the consumption of A4 paper.

Therefore, taking good use of the paper on your desk, not wasting it, is the protection of nature. It is also the responsibility of each of us.

Save Paper, Save Trees
Save Paper, Save Trees – Originally from lifeadvancer.com

Here you can find the dynamic paper consumption status and Hectares of forests cut down of this year.

Main Facts of A4 Size

A4 Dimensions in inches, mm, cm
in inches: 8.27″ x 11.69″
in mm: 210 x 297 mm
in cm: 21.0 x 29.7 cm

Area: 1/16 square meter.

Country of use: Most countries except North America

Other name: DIN A4 Size

Usage: Office paper in most countries in the world.

Advantages: Suitable size for office and document signing, easy binding and carrying; No customization required, can be used in most countries internationally..

Disadvantages: Not suitable for use in American countries.

Ratio: It follows the ratio of ISO216 size standard, length to width: 1.414:1, or √2:1.

Approximate American size: Letter paper size, measures 8.5″ x 11″ in inches, 216 x 279 in mm, or 21.6 x 27.9 in cm, and is slightly wider and shorter than the A4 size.