International Standard Paper, and Why You Don’t Know About It

This might just be our nerdiest blog yet, and on a blog dedicated to teaching you the nitty gritty of the printing industry, that’s saying something. We’re going to dive into math, history and the metric system today, while we explore something not a lot of people know about in North America; International Standard Paper Sizes, how they work, why they work, and why we don’t use them.

The metric system was made on a key principle: that everything in the system should translate easily to another element in the system. Water, being the most common element, was used as a key point; one litre of water weighs one kilogram, allowing a transfer from volume to weight. In a similar manner, water boils at 100 Celcius, and freezes at 0. The prefixes for the metric system are also easy to understand. Paper manufacturers wanted to have the same level of ease when transferring from paper size to paper size, so International Standard Paper Sizes were born.

The first size of paper is known as A0; it’s not the most practical size for most people’s purposes, but it does have an important quality; it’s surface area is almost exactly 1 square metre. A0 papers are 841 mm by 1189 mm, which is 0.999949 square metres. Why not have it be exactly 1 square metre? That’s because if you divide 1189 by 841, you end up with the square root of 2. Why do we care about that ratio? Well, because it’s got a particularly interesting property; if you divide it in half, so that it’s longer side is divided in two, you end up with the same ratio. Take 1189, divide it by two, and you get 594; 841/594 is again the square root of two. The same thing holds true, of course, if you double the shorter side. That means that an A1 paper is just an A0 paper divided in two; the same holds true for A2, A3, etc.

So why do we have totally different standards in North America? The answer may be that we’ve got an aversion to the metric system, though less so here in Canada. There are apocryphal tales about how the letter-size standard became standard; some say it’s because of how paper had to be manufactured in old paper mills. The Canadian government tends to use the International Standard, but most documents created by citizens just use the letter-size standard, as does the United States, the Philippines, and parts of Mexico.

Now you know way more about paper sizes than you ought to. This could be a fun experiment for kids, so long as you can procure some of that rare, international paper; fold some in half, double it up, and teach them about irrational numbers! That, or you could visit Winnipeg printers who will help you pick the perfect size, without getting into all the math; it might be a bit simpler!