A manuscript is the source text that forms the basis of a publication or broadcast. In the era of pen and paper, manuscripts were handwritten on genkouyoushi (manuscript paper); today they are composed in text editors and word processors. The expression "X sheets of manuscript paper" remains a standard way to describe text volume in Japanese, with the 400-character sheet as the base unit.

A standard 400-character sheet of genkouyoushi has a grid of 20 characters by 20 lines. A 200-character variant (20 characters by 10 lines) also exists, but the 400-character format is the norm. "Five sheets of manuscript paper" means 2,000 characters; "ten sheets" means 4,000. School composition assignments, essay exams, and literary prize submission guidelines in Japan frequently specify text volume in these units.

Counting characters on manuscript paper follows its own set of rules. Punctuation marks occupy one square. When a punctuation mark falls at the end of a line, it is tucked into the last square alongside the preceding character (a technique called "burasage," or hanging punctuation). The first line of a paragraph is indented by one square. Opening brackets may appear at the start of a line, but closing brackets must not (a rule known as "kinsoku" processing). These rules mean the actual number of writable characters is somewhat fewer than 400.

In the digital age, character-count management has become far more precise. A text editor's character-count feature lets writers check their count in real time. However, the "manuscript-paper equivalent" count and the actual character count do not always match. On manuscript paper, the remaining squares after a line break count as blank space, whereas a digital character counter treats a line break as one character (or zero characters).

In the publishing industry, a manuscript's character count directly determines the number of pages and the price of a book. A typical paperback page holds about 600 to 700 characters (40 to 43 characters by 16 to 17 lines), so a 200-page paperback contains roughly 120,000 to 140,000 characters. A standard "shinsho" (pocket-sized nonfiction) runs 80,000 to 100,000 characters, and a business book 60,000 to 80,000. Manuscript commissions specify the target in units of ten thousand characters.

For web content, character count is an important metric from an SEO perspective. Content that ranks highly in Google search results typically contains 2,000 to 5,000 characters of substantive material. That said, more characters do not automatically mean better results; the prerequisite is high-quality content that accurately addresses the reader's search intent. Writing guides on Amazon offer practical advice on structuring manuscripts for both print and digital.