A3 paper size Guide. 

The A3 paper size, as with others in the ‘A’ range, was standardised in 1975 by the international convention ISO 216. With dimensions that makes it a particularly diverse paper format, we’ll review its primary characteristics - and explore how big A3 paper really is.

A3 paper dimensions.

A3 paper size measurements are 297 mm x 420 mm, 29.7 cm x 42 cm or 11.7 in x 16.5 in. Its printing surface is large enough for everyday use at 0.125 m² or 1250 cm².

This table shows that the standardisation of these formats maintains their proportions when a sheet of paper is cut or folded in two. The relationships between the sizes are as follows:

• A3 = ¼ of A1

• A3 = ½ of A2

• A3 = 2 x A4

• A3 = 4 x A5

Printing with A3. 

Whether used in a professional capacity or for personal use, printing photos or other designs in A3 is very popular. During the creation of the source file, the resolution is defined and changes the A3 format to pixels:

• For an image with a resolution of 300 dpi (dots per inch), you will need a size of 3508 x 4961 pixels per inch.

• For an image in 200 dpi, you will need 2339 x 3307 pixels per inch.

• To print an image in 100 dpi on A3, you will need a size of 1170 x 1654 pixels per inch.

If you have an A3 or A4 printer available to use, you must then prepare your file and add a 3 mm bleed margin to your document to avoid losing some of the visual in printing. You should also adapt the size and resolution of the image. 

Although copiers and domestic printers are improving every year, asking the advice of a printing professional for scanning on A3 sized paper can also be helpful. They can advise you on the best type of paper to use for the most professional and high-quality outcome.

A3 paper size: the ideal format to develop creativity.

A3 sized paper is just as popular among professionals as it is among individuals. It has a wide range of possible uses.  

The versatility of A3 makes it a common format in creative industries including photography. Page layout software InDesign offers a huge variety of options for visual creations and the design of printed posters.

Frequently asked questions. 

What’s bigger - A3 or A5?

The A3 paper size is bigger than A5. A3 is 297 mm x 420 mm whereas A5 is 148 mm x 210 mm. The smaller the number in the A paper size format, the larger it is. That’s why A0 is the largest paper size in the format. A5 is a quarter the size of A3.

Why does the US use different names for its paper sizes?

North America is among only a few remaining countries that don’t use the A series as its standard for paper sizes. Other countries include:

• Canada

• Mexico

• The Philippines

• The Dominican Republic.

In North America, the closest type to A3 size paper is called Tabloid or Ledger. It measures 279 x 432 mm.

What is the A3 paper size used for?

Due to its rather large size, A3 paper is often used in industries that require diagrams, including engineering and science. It’s also popular in the office environment and schools, for presentations and posters.

As A3 can be halved to create two A4 pages, it’s also useful for leaflets and restaurant menus.

Find out more about paper types and graphic design.

• Paper formats
• A4 format
• A5 format
• A6 format