A history of A4 and Letter paper sizes

Paper sizesWhether using Serif products or not, the vast majority of us will have encountered documents in both A4 and Letter sizes.

Even when documents are made for digital distribution, many still have a size and shape that ties them to the real world of printing on paper.

A4 and Letter paper sizes are similar, but why do both standards exist? Get comfy for a quick look into their history…

The A-series

A4 (21cm x 29.7cm or 8.25″ x 11.67″) doesn’t jump out as an obviously neat imperial or metric measure, but A4 is part of an official metric standard. It was set in 1975 and is based on a German standard originally from 1922. The key feature of this paper size is that A4 is half the size of A3, which in turn is half the size of A2 and so on up to A0, the largest in the range.

At 84.1cm x 118.9cm, A0 is exactly 1m2 of paper. As metric paper weights are usually measured in grammes per square metre (gsm), this doubling/halving relationship between each size makes mass calculations very easy when dealing with large volumes of paper in the print and publishing industries. This gives the A-series of paper another great trick up its sleeve that saves printers and designers some major headaches…

A0 paper is 1 metre squared in area, so why isn’t it just 1m x 1m for ease? Because when a 1m x 1m square is halved (the most cost-effective way to produce new sizes from large paper sheets), the new rectangular size no longer has the same shape as the original – any artwork resized during reproduction wouldn’t fit the page properly. Not helpful. Halve the paper size again and it becomes square again, so there would be two very different shapes of paper throughout the range. For A-series paper, smaller sizes are exactly half the previous paper size in every case, and importantly they are also exactly the same shape from one size to the next, with a width-to-height ratio of 1:1.41.

This means an A4 page can be scaled up by 41% and all the artwork and text is the perfect width and height to fill an A3 page. Similarly, scaling A4 artwork down to 71% of its original size will see it fit perfectly on an A5 page with no unpleasant stretching, squashing, or redesigning of artwork required (Note that PagePlus and other apps can perform this scaling automatically on output). This “magic number” for paper aspect ratio, 1 to the square root of 2, was first suggested way back in 1786.

Letter paper

US office with letter sized paperLetter paper, common throughout the USA, Canada, Mexico and a few other countries, at 8.5″ x 11″ (21.6cm x 27.9cm), is a similar shape to A4 but slightly wider and slightly shorter.

Although in use for some time, it only became a recognised standard in 1921 to reduce waste in industry. At the same time, the US government chose another standard for official use, a slightly smaller page. Letter paper didn’t become the official national standard size for US government until the early 1980s!

The largest paper size in the popular range, 17″ x 22″ (4 times bigger than Letter), was a legacy from manufacturing limitations of a few hundred years ago when paper was made by hand, and was determined by what humans can achieve with an average arm length. From this large size, the paper was halved and quartered to make modern Tabloid (11″ x 17″) and Letter (8.5″ x 11″) sizes. The early days of print are a rich heritage, but Letter paper may not survive globalisation.

Unlike the A-series paper sizes, this older range doesn’t quite have a “magic number” aspect ratio to make the range’s sizes all exactly the same shape as each other – but they are not so different as to make things unworkable when switching from one size to the next. As global business and information sharing is all on the up, and many of us are still printing business documents, the A-series is still increasing in popularity in North America and elsewhere. It may still become a global standard in future, but until then we’re pleased to say that Serif’s design software supports a range of sizes and document types to suit a massive variety of needs, with modern digital output that can negate printing completely.

But, who needs paper?!

Documents, eBooks, eMagazines, eBrochures and articles are increasingly viewed on screen rather than printed, and PagePlus excels at creating and optimizing this kind of output, including rich multimedia content like videos and interactive buttons, forms and more. With some content that reflows to suit the viewer’s preference and some that retains a paper-like document shape, whether browsing a brochure after quickly downloading it from the web or learning with a white paper on an eBook reader, there will be some who wish they were holding paper versions instead! For all those people as well as those who believe paper is ‘already dead’, you now know why some popular documents are 21cm x 29.7cm and others are 8.5″ x 11″!