A4 – ISO paper sizes A series formats

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 are defined in ISO 216 by the following requirements:

• The length divided by the width is 1.4142
• A0 size has an area of 1 square meter.
• 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 millimeter.

Note: For reference the last item is there because the root 2 aspect-ratio doesn’t always give a whole number.

RA & SRA Untrimmed Sizes

RA & SRA sizes define untrimmed paper for commercial printing. These formats are designed to allow for ink bleed during the printing process so that the paper can then be trimmed to one of the A series sizes.

A3+ or Super A3 Format

A3 Plus, or Super A3 as it is sometimes known, is not an ISO 216 paper size. It has dimensions of 329mm x 483mm (13″ x 19″). This gives it an aspect ratio of 1:1.468 rather than the 1:root 2 aspect ratio of the ISO series paper sizes. In actuality the A3+/Super A3 name is quite misleading as this paper size is known as B+ or Super B in the United States and is ANSI B with a 1″ margin for print bleed.

4A0 & 2A0 – DIN 476 Oversize Formats

The paper sizes bigger than A0, 4A0 & 2A0, aren’t formally 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. 2A0 is sometimes described as A00, however this naming convention is not used for 4A0.

ISO Guidelines

ISO 216 specifies international standard (ISO) paper sizes used in most countries in the world today, although not in Canada, the United States, Mexico, Colombia, or the Dominican Republic. The standard defines the “A” and “B” series of paper sizes, including A4, the most commonly available paper size worldwide. Two supplementary standards, ISO 217 and ISO 269, define related paper sizes; the ISO 269 “C” series is commonly listed alongside the A and B sizes.

All ISO 216, ISO 217 and ISO 269 paper sizes (except some envelopes) have the same aspect ratio, √2:1, within rounding to millimetres. This ratio has the unique property that when cut or folded in half widthways, the halves also have the same aspect ratio. Each ISO paper size is one half of the area of the next larger size in the same series.

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 formerly used British Imperial sizes. In Europe the A paper sizes were adopted as the formal standard in the mid 20th century and from there they spread across the globe.