12: 260×250 (mm mm)

For the text of a book, the meaning of the folio number is the same as that of the folio number, but for the folio number of the cover and the insert, the meaning is different because of the different areas. Usually, the size of a single-page publication is called folio, such as newspapers and wall charts, which are divided into full page, folio, 4 page and 8 page.

Because there are several different series of paper formats at home and abroad, although they are all cut into the same size, but the specifications are different. Although bound into a book, they are collectively called how many folio, but the size of the book is different.

Extended data:

At present, the format specifications of books and periodicals are mainly series specifications, as follows:

a4( 16k)297mm×2 10mm； a5(32k)2 10mm× 148mm； There are three models of A6 (64k)144mm×105mm, of which A3(8k) has not been determined, but 420mm×297mm is widely used.

Commonly used format size:

8 format: 374×262mm, small 8 format: 368×260mm；; ;

Large 16 format: 262× 187mm, small 16 format: 260×184 mm;

Big 32 format: 203× 140mm, small 32 format:184×130mm;

Big 64 format:13/kloc-0 /×101mm or 130×99mm,

Small 64 format: 127×95mm or 125×92mm.

References:

Baidu encyclopedia-folio size