The B-series standard, which ranges from B0-B10, is based on a 1.5㎡ sheet (B0, or full B sheet) with each successive size defined as half of the preceding size, dividing the sheet in the middle of the longer side. The ratio of the length of the short side to that of the long side is 1: √2.

The standard measurements for Japanese paper were established as part of the JES (Japanese Engineering Standards) in 1929. After World War II, these standard were maintained (with slight modifications) as the JIS (Japanese Industrial Standards), which became the present-day specification for “Writing paper and certain classes of printed matter—Trimmed sizes.”

The B-series Japanese paper measurement standard is particular to Japan, having its origin in the Minoban format of Mino paper, which was an official paper during the Edo period (1603-1868). It is because of these origins that B-series paper was used in government offices until 1993, when the A-series was adopted to conform to international standards.

When producing printed matter, it is necessary to print a crop mark to designate the edge of the finished product. For this reason, one uses extended A3-size paper to print B4-sized material. When printing B0-sized material, one uses extended B0-size paper, which is oversized to allow for crop marks. Extended sizes vary depending on the paper manufacturer.