B Series

ISO 216 Standard and the B Series

The ISO 216 standard defines the B series, which serves as a complementary set of paper sizes. It was created to provide a wider range of dimensions that the A series doesn't cover, ensuring there is a standardized size for almost any professional printing requirement.

Main Characteristic

The B series shares the same aspect ratio of 1:√2 (approximately 1:1.414) as the A series. This means it retains the "halving" magic: folding a B-series sheet in half results in two sheets with the exact same proportions.

The genius of the B series lies in its relationship to the A series. A B-series size is the geometric mean of the A-series size of the same number and the A-series size one step above. For example, the dimensions of B1 are between A0 and A1. This makes the B series ideal for tasks where an A-size just doesn't quite fit, such as posters, books, or envelopes.

Measurement System

Starting Point: Unlike the A series (which starts with a 1m² area), the B0 size is defined by its width. A sheet of B0 is exactly 1 meter wide (1000 mm). Given the 1:√2 ratio, this results in a height of 1414 mm.

Scaling: Just like the A series, every subsequent size is half the area of the previous one. B1 is half the area of B0, B2 is half of B1, and so on.

Common Usage: You’ll most frequently encounter B5 (176 x 250 mm) for notebooks and printed books, or B2 and B1 for high-impact posters and maps. Because B-series sheets are slightly larger than their A-series counterparts, they are often used by printers to allow for "bleeds" and trim marks.