D4

With dimensions of 192 mm by 272 mm, the D4 format defined in the German DIN 476 paper size standard falls between ISO A5 and A4 in size. Its 0.052 square meter area facilitates general office use bridging notes and correspondence to larger administrative documents. In particular, the elongated proportions with a width-to-height ratio of 1.25 suit internal technical specifications passed between departments with the military and engineering sectors. The UK "Foolscap Quarto" sheets match D4's size quite closely as well.

Likely adapted from existing regional formats, D4's landscape dimensions fill a void between standardized dimensions like A4. The width aligns segmentation needs of long tables and charts requiring more columns than the narrow ISO 216 sizes. D4's roots perhaps originate from traditional German printer paper dimensions. Nonetheless, as A4 and A5 achieved widespread adoption in industries and governments, the niche D4 format saw declining use by the latter 1900s despite its inclusion as a complement to A, B, and C sizes in DIN 476 since its 1922 publication.