A2.1

The A2.1 is an elongated ISO 5457 paper size that combines the 420 mm short side of an A2 sheet with the 841 mm long side of an A1 sheet. This results in the A2.1 having dimensions of 420 mm x 841 mm. With an aspect ratio of 2:1, the A2.1 is twice as long as it is wide. The total surface area of an A2.1 sheet is 353,220 mm2 or 0.3532 m2.

As with the other ISO 5457 elongated sizes introduced in 1999, the A2.1 aims to add flexibility while maintaining A-series width-to-length ratios. The motivation was that some technical drawings and designs benefit from a particular elongated orientation fitting on a longer sheet at standard proportions. The A2.1 allows for this with its 841 mm length compared to the 594 mm of a standard A2. The ANSI/ASME Y14.1 standard adopted the A2.1 and other ISO 5457 sizes for use in the United States in addition to the normal A2 and other A-series formats. In summary, the A2.1 provides an elongated dimension for narrow A2-ratio drawings while keeping the familiar ISO A-series proportions.