B5 paper is equivalent to a Chinese textbook, and B5 paper refers to the size of B5 paper. B5 generally has two sizes, EXTRA, that is, the international standard size 176mmX250mm, which is universal. The specification of paper refers to that after the paper is made, it is trimmed and cut into a certain size.

According to the national standard 1965, the layout of books and periodicals is divided into three groups: A, B and C. The original paper of 841mm×1189mm is cut in group A, and1000mm×1469mm is used in group B. 1982 and GB 788-87 emphasize the adoption of international standards. The new standard retains the A series in the old standard, adopts the B series in the international standard, and cancels the folio of B and C in the original standard. Its purpose is to promote foreign trade and international exchanges. A4, B5, etc. That is, when we usually copy it, it is an international standard.