A3 paper size and dimensions: everything you need to know

We explore A3, the fourth paper size in the ISO 216 A series.

A3 paper is double the size of by far the most common size, A4, and is used in numerous settings. Since A3 is so popular, it’s worth knowing its dimensions and most widespread uses.

In this article, we’ll discover what ISO 216 is, the size of A3 paper in centimetres, inches and pixels, and how the grammage can affect the end result in the printing process. We’ll finish off with a few hints on how best to print advertising materials in A3 format.

Let’s get started!

A3 paper: dimensions and weight

As we hinted above, ISO 216 is a set of regulations that establish the standard dimensions of sheets of paper, in three categories: A, B and C, each of which is in turn divided into 11 subgroups. In the A series, a sheet of A3 is the equivalent of one-eighth of a sheet of A0.

Without further ado, let’s have a look at the size in centimetres, inches and pixels of each A series paper size.

A3 paper measures 29.7 x 42 cm, i.e. 297 x 420 mm, or 11.7 x 16.5 inches.

The number of pixels, meanwhile, depends on the resolution, which is measured in dpi. The higher the resolution, the higher the pixel count. For example:

72 dpi: 842 x 1,191 px

150 dpi: 1,754 x 2,480 px

300 dpi: 3,508 x 4,960 px

600 dpi: 7,016 x 9,933 px

The weight of sheets of A3 paper also varies, and depends on the grammage or basis weight of the paper – how thick it is, in other words. A sheet of 80 gsm A3 paper will weigh 10 g, a sheet of 100 gsm A2 paper will weigh 12.5 g and a sheet of 160 gsm paper will weigh 20 g.

Here is a table summarising the dimensions for the entire A series of paper sizes in millimetres, inches and pixels when printed at 300 dpi.

Paper size	Millimetres	Inches	Pixels (300 dpi print quality)
A0	841 x 1,189	33 x 47	9,933 x 14,043
A1	594 x 841	23 x 33	7,016 x 9,933
A2	420 x 594	16.5 x 23	4,961 x 7,016
A3	297 x 420	11,5 x 16,5	3.508 x 4.961
A4	210 x 297	8.3 x 11.7	2,480 x 3,508
A5	148 x 210	5.8 x 8.3	1,748 x 2,480
A6	148 x 105	5.8 x 4.1	1,240 x 1,748
A7	105 x 74	4.1 x 2.9	874 x 1,240
A8	74 x 52	2.9 x 2.0	614 x 874
A9	52 x 37	2.0 x 1.5	437 x 614
A10	37 x 26	1.5 x 1.0	307 x 437

Table of dimensions for A series paper sizes in millimetres, inches and pixels

A3 paper: what is it used for?

A3 paper is exactly double the size of a standard sheet of A4 printer paper.

A3 is used for printing many of the posters you see advertising various things in shop and office windows. Sheets of A3 paper are also very commonly used in photography and advertising, including for folded leaflets and flyers. Anyone who grew up in Italy will also remember the classic Fabriano pads of A3 drawing paper, a primary school staple, on which every Italian child is let loose with crayons and paints.

A3 paper: resolution and printing tips

A3 paper is often used for printing promotional materials, as it is easy to turn it into flyers and brochures. There are many different pieces of software available for producing advertising materials like leaflets and flyers yourself. It is vital you check the preview of your brochure before sending it for printing, and don’t forget to leave a small (2-3 mm) margin or bleed in the graphic file, to ensure the print is not spoiled by small blemishes.

You’re now armed with everything you need to know about A3 paper: time to use it in your projects and unleash your creativity!

Best of luck!