See also https://www.explainxkcd.com/wiki/index.php/2322:_ISO_Paper_Size_Golden_Spiral https://www.explainxkcd.com/wiki/index.php/2322:_ISO_Paper_S... Europea

See also https://www.explainxkcd.com/wiki/index.php/2322:_ISO_Paper_Size_Golden_Spiral https://www.explainxkcd.com/wiki/index.php/2322:_ISO_Paper_S... European paper sizes are based on a sqrt(2) spiral so cutting in half works well.