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WonderStandards design fact

Cut an A4 sheet in half across its length and you get two A5 sheets with exactly the same proportions. This works because the international paper standard ISO 216 sets the sides in a ratio of 1 to the square root of 2, about 1 to 1.414.

ISO 216

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The story behind the card

The idea is old. The German scientist Georg Christoph Lichtenberg pointed out the advantages of the square-root-of-two ratio in a letter in 1786, and revolutionary France listed similar formats in a tax law of 1798. The modern system came from the German engineer Walter Porstmann, whose proposal became the German standard DIN 476 in the early 1920s and later the international standard ISO 216. The largest size, A0, has an area of one square metre; A1 is half of it, A2 half again, and so on down to A4 and beyond. Because every size has the same shape, a page can be enlarged or reduced on a photocopier without cropping. The main countries that still mostly use other sizes, such as Letter, are the United States and Canada.

Türkçe oku
A4 bir kâğıdı uzun kenarının ortasından ikiye kestiğinizde, oranları birebir aynı iki A5 yaprak elde edersiniz. Bunun sırrı, uluslararası kâğıt standardı ISO 216'nın kenarlar arasında kurduğu orandır: 1'e karekök 2, yani yaklaşık 1'e 1,414.

Fikrin geçmişi eskidir. Alman bilim insanı Georg Christoph Lichtenberg, karekök 2 oranının avantajlarına 1786'da bir mektubunda değinmiş, devrim dönemi Fransa'sı da benzer ölçüleri 1798 tarihli bir vergi yasasında sıralamıştı. Bugünkü sistem, Alman mühendis Walter Porstmann'ın önerisine dayanır. Bu öneri 1920'lerin başında Alman standardı DIN 476 olarak yürürlüğe girdi, ardından uluslararası ISO 216 standardına dönüştü. En büyük boy olan A0'ın alanı bir metrekaredir; A1 bunun yarısı, A2 onun da yarısıdır ve dizi A4'e, oradan daha küçük boylara iner. Bütün boyların biçimi aynı olduğu için bir sayfa fotokopide kırpılmadan büyütülüp küçültülebilir. Bu standart yerine hâlâ çoğunlukla Letter gibi başka ölçüler kullanan başlıca ülkeler ABD ile Kanada'dır.

Sources and further reading

Background reading: ISO 216
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