Industrial paper is measured by meters, but everything else such as type size, image resolution, etc is based on inches. Although it’s not really difficult to make the different units coexist on a paper as long as you are fine with fractional measurements, wouldn’t it make more sense to just use metres for type size too? Are you really comfortable with making a point-based grid on a metre-based paper?
In fact, there is a country that uses metric type size, and it’s called Japan. The unit is called Q or q, which is a quarter of a millimetre (0.25 mm), a little finer than a DTP point (0.3528 mm), and was invented in the phototypesetting era. There is also a unit called Ha (or simply H or h), which is basically the same as Q but used for anything other than type size (e.g. line spacing). Ha means a tooth of a cog. Older phototypesetting machines had a big drum where a photographic paper would be attached, on which the operator would expose a photographic image of a letter, dot, line, etc., and the rotation of the drum by one unit (or a cog) would move the paper by 0.25mm. Hence the term.
Okay, let’s to some math.
4 Q equals to 1 mm.
12 Q is 3 mm.
10 points (3.528 mm) is around 14 Q (3.5 mm).
12 points (4.2336 mm) is around 17 Q (4.25 mm).
When you want to use what is closest to 12 points in the Q-based layout (17Q), the size is an odd number and thus makes you slightly less comfortable , but in this case you should perhaps give up on 12 points and use the even-number size if you want to avoid quarter millimetre unit. Personally speaking, sticking to even numbers is easier to control the layout; making a grid based on 17 Q sounds a bit complicated to me and 16 Q (4 mm) sounds easier. If you are a good typographer, you know that those numerical size doesn’t assure the appearance of the fonts and 12 points doesn’t mean anything anyway. Another advantage apart from its metric nature is that there are more steps in Qs than points, which allows finer control without going too fractional.
The Q&Ha system (or just Q) is especially suited for Japanese typography because almost all typefaces were designed in the square; proportional Japanese fonts have been rare, especially in the phototypesetting era. It was therefore quite easy to accurately measure the line length (character count per line) and compose a typographic grid from head to toe without dealing with fractional numbers, also because industrial papers are measured by meters as mentioned earlier. It is still and quite commonly used by professional typographers graphic designers.
Which application actually supports it? All publishing software and word processor in Japan only use points by default, but some applications such as the CJK version of Adobe CS/CC, Quark, TeX do support Q&Ha. This means that US/Euro versions of InDesign don’t support it; oddly enough, they only support points and pixels (whiskey tango foxtrot). To make matters even sillier, Illustrator supports points, inches, Qs, millimetres, and pixels (it supports vertical text layout too). US/Euro Illustrator is actually better than InDesign as a CJK typesetting app (not just because it supports other units, but that can take another blog post to explain).
As it is not supported by the major applications (i.e. MS Office), Japanese people only use points without knowing what it is, and Q&Ha only remains as a unit for professional typesetters. As Japan otherwise uses meters almost all the time, except in golf and screen measurement I guess (and bicycle wheel), it would be nice to have a option to use metres. When I learned about it in the art university, everything started to make sense. It just felt so much better than points.
Despite my hope that everyone should use Qs, its status will probably remain the same as it is now. It will survive strongly in Japanese typography, and will stay only in Japan too. After all, it’s only a type size and what really matters is how big or small the text looks. But for those who seek perfect grid in print typography, the Q system may be one way to go. And Adobe and Microsoft, please support it in your applications.