Metric typographic units

ADVISORY: the information contained in this article appears to be largely inaccurate and derived solely from the also inaccurate Web page cited in the External Links section. The sizing of current digital fonts can be specified in millimeters rather than points in many page layout applications, and with CSS for Web design. No standards need be adopted or implemented for this. The description of the DIN 16507-2 system here also appears highly flawed.

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Most desktop publishing software, coming from the US, such as Adobe PageMaker and QuarkXPress and Adobe InDesign, uses the PostScript point as the unit of measurement for typography. PostScript points are defined as 1/72 of an inch, which is 0.3527777778 millimetres in SI. In the push towards metrication of all standards throughout the world, a metric standard has been devised for typography.

DIN 16507-2

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DIN, the German standards body, has devised a standard way of specifying font dimensions in metric units using two values: font size (Schriftgröße) and font height (Oberhöhe). The latter is the height of a full-height letter, such as H, and the former is, by default, 72% of it (rounded) for well-proportioned, one-line leading. Font dimensions are specified in two numbers separated by a solidus: SG/OH, both in millimetres. For example, a text in about 12pt size and with default, one-line leading is defined as 4.3/6.0 according to the standard. The same size with extra leading, for one and a half lines of space, is defined as 4.3/9.0. Text in about 14pt size and default leading is 5.0/7.0.

The German standard can already be used today in web design in CSS rules, for example:

body { font: 4.3mm/6.0mm "Times New Roman", times, serif; }

or

h1 { font-size: 8.6mm; line-height: 12.0mm; }

Other proposals

The DIN standard uses the H-height for the second value, but some typographers have proposed using the x-height instead.

Device resolutions in metric

Computer screens and office printers usually denote resolution in dots per inch (dpi), but phototypesetters have long used micrometres (μm). To convert dpi resolution to μm resolution, the formula to be used is simply 25400 / R , where R is the resolution in dpi. So for example 76dpi translates to a resolution of 334.21 μm.

The CSS3 media queries standard uses a unit dpcm (dots per centimetre) for resolution.