Here is a useful reference for A paper sizes in mm or A paper dimensions in inches. So you can easily find out A4 in cm, A3 in inches, A3+ in mm

Sizes include A0, A1, A2, A3, A3+, A4, A5, A6, A7, A8, A9, A10 in centimeters, inches and millimeters.

Dimensions of International ‘A Series’ Paper Sizes as defined by ISO 216

Here is a table containing the dimensions of the A series paper sizes.

Dimensions are given in the table below in millimeters, centimeters and inches.

Table of Paper Sizes From 4A0 to A10

 Size Height x Width (mm) (cm) (inches) 4A0 2378 x 1682 mm 237.8 x 168.2 cm 93.6 x 66.2 in 2A0 1682 x 1189 mm 168.2 x 118.9 cm 66.2 x 46.8 in A0 1189 x 841 mm 118.9 x 84.1 cm 46.8 x 33.1 in A1 841 x 594 mm 84.1 x 59.4 cm 33.1 x 23.4 in A2 594 x 420 mm 59.4 x 42.0 cm 23.4 x 16.5 in A3+ 483 x 329 mm 48.3 x 32.9 cm 19 x 13 in A3 420 x 297 mm 42.0 x 29.7 cm 16.5 x 11.7 in A4 297 x 210 mm 29.7 x 21.0 cm 11.7 x 8.3 in A5 210 x 148 mm 21.0 x 14.8 cm 8.3 x 5.8 in A6 148 x 105 mm 14.8 x 10.5 cm 5.8 x 4.1 in A7 105 x 74 mm 10.5 x 7.4 cm 4.1 x. 2.9 in A8 74 x 52 mm 7.4 x 5.2 cm 2.9 x 2.0 in A9 52 x 37 mm 5.2 x 3.7 cm 2.0 x 1.5 in A10 37 x 26 mm 3.7 x 2.6 cm 1.5 x 1.0 in

Example: A4 in cm = 29.7cm x 21cm, A4 in inches = 11.7 x 8.3, A4 in mm = 297mm x 210mm

A popular size for printing is A3+. A3+ in mm = 483mmx329mm

The A Series paper size chart below visual explanation of how the sizes relate to each other – for example A4 is half of A3 size paper and A1 is half of A0 size paper.

A Series Paper Sizes Chart – A0, A1, A2, A3, A4, A5, A6, A7, A8

4A0 & 2A0 – The DIN 476 Oversize Formats

The paper sizes bigger than A0, 4A0 & 2A0, aren’t formerly defined by ISO 216 but are commonly used for oversized paper. The origin of these formats is in the German DIN 476 standard, that was the original base document from which ISO 216 was derived.
A Series Paper Size Tolerances

ISO 216 specifies tolerances for the production of A series paper sizes as follows:

±1.5 mm (0.06 in) for dimensions up to 150 mm (5.9 in)
±2 mm (0.08 in) for lengths in the range 150 to 600 mm (5.9 to 23.6 in)
±3 mm (0.12 in) for any dimension above 600 mm (23.6 in)

A Series Paper Sizes Defined

The A series paper sizes is calculated by the following format:

The length divided by the width is 1.4142
The A0 size has an area of 1 square metre.
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 is rounded to the nearest millimetre.
International Usage

The A series paper sizes are now in common use throughout the world apart from in the US, Canada and parts of Mexico. The A4 size has become the standard business letter size in English speaking countries such as Australia, New Zealand and the UK, that used to use British Imperial sizes. In Europe the A paper sizes were adopted as the formal standard in the mid 20th century.

So now you can easily find A4 size in mm, A4 in cm, A3 size in cm, A4 in inches or A3 in inches, A3+ in mm with this useful A paper size reference guide.