ASTC Insights 


How did the French Revolution impact technical writing today?

​A brief history of A4 paper

With the majority of technical publications now consumed online, it is easy to forget the fascinating history behind our standard paper sizing.

By Jason Xiros

Rising social and economic inequality in France eventually led to civil unrest and revolt during the late 1700s

Not only were the ruling bourgeoisie overthrown, it was seen as opportunity to overthrow old ideas, and the metric system of measurements quickly rose to prominence.

Not long after introducing the meter measurement, the French government published a 1798 tax law “Loi sur le timbre” (no. 2136) that defined several paper formats. These correspond almost exactly to the modern ISO sizes:

  • “grand registre” = ISO A2

  • “grand papier” = ISO B3

  • “moyen papier” = ISO A3

  • “petit papier” = ISO B4

  • “demi feuille” = ISO B5

The French format series never became widely known and was quietly forgotten.

The principle behind them however was mathematical, and our modern A, B, and C series paper formats were independently reinvented over a hundred years later by Dr. Walter Porstmann in Germany.


The magic aspect ratio (1:1 to √2)

The base A0 sheet has an area of exactly one square metre.

In the ISO paper size system, the height-to-width ratio of all pages is then the square root of two (1.4142 : 1).

In other words, the width and the height of a page relate to each other like the side and the diagonal of a square.

Each paper size is exactly half the size of the previous sheet:


Why is that so important? It means the aspect ratio is not compromised as you scale from one size to another. This is critical when reproducing graphics and images... they will scale up or down without distortion.

Any copier or printer can simply reduce a page from A4 to A5, or enlarge a page from A4 to A3. Similarly, two sheets of A4 can be scaled down to fit one A4 sheet without waste.

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