In typesetting and office software, Song Xiaosi's font size is a conventional font size specification, which represents the specific font size. In China's traditional typesetting industry and modern computer document editing, the Song four-body corresponds to the number "12", and the height of the Song four-body is about12kg.

This font size is widely used in office documents, book typesetting, academic papers and other fields. Because of its moderate size and good reading experience, it has become a common font specification in standard document formats.