What size of type is commonly used in Japanese books, magazines, or in blocks of online text? Since there is unlikely to one single size, I'd welcome an answer that either gave a rough range or listed a couple specific examples from major presses, newspapers, or websites.
(I am asking because I'm curious about whether the complexity of kanji leads to larger type than the type sizes that are standard for works produced with roman letters.)
Typical main text of a paperback targeted to adults uses a font size between 8 and 9 pt. Most newspapers use 8.6 pt (≒3 mm). In footnotes or such, as small as 5 pt is possible.
Websites use larger fonts. Condensed pages like Yahoo! home use 12px (9pt), but most recent sites prefer 16px (12pt) or so for main text. From what I understand, most global websites (like Twitter) use the same font-size setting for their Japanese and English versions.
The smallest font size which is practically readable is 9 pixels (this was common in the Windows 3.1 / Mac OS 6 era), but there is even a 7 pixel font.
Ordinary publications use fonts around 11Q to 16Q big for main text. The unit Q (級) is the standard measure in Japanese typesetting industry, being 1/4 length of a millimeter (Q is from Quarter). Thus 11Q = 2.75mm ~ 7.8pt, 16Q = 4mm ~ 11.4pt. The default font size of MS Word is set to 10.5pt in Japan.
Actually, since Japanese characters don't have ascenders and descenders like European letters, each letter is designed to cover up almost full body height, so that they usually look one or two sizes larger than European ones with the same nominal size. In exchange, we tend to need taller line spacing than European books. Optimal line height is 166% (12⁄3) to 200% of the font size. Compare page layouts of a Japanese and an American paperback.
The websites usually prefer slightly larger fonts than Western average if possible, because of the pixel density matter. For example, current text font-size and line-height of Japanese WP are set to 15.1px/24.2px while the English version is 14px/22.4px.
