The unit is used em in the pleading to determine the character width depending on the font size. An em is the width of an em (English quad ) of the pressure system. That is, although it is claimed widespread, not exactly - but only about - the width of the capital letter M. The width of the fourfold corresponds to the height of the fourfold and thus the font size - an em is thus directly proportional to font size, regardless of the design of the capital letter M of the respective font. For the semi- em en stands.
In the representation of text documents, two criteria show concerning the width of a column that facilitate or impede the reader reading a text:
- Too long lines make it difficult to find the next line after the line break.
- Short lines lead to larger voids at the ends of lines.
A pleasantly readable typeface can be defined independent of the font size by defining the width in em. With the size of the font, the length of the line, making the typeface remains changes.
Use in web representations
Even with the appearance of Web pages, the em unit is significant. Regardless of browser - based settings, the font size, the appearance of the text can be defined by the web designer, as opposed to absolutely defined widths, which may occur in extreme cases above-mentioned problems.
The significant for the design of web pages CSS standard does not define an em but the width of the letter M, but as the current font size of the font in pixels.
Em can be used in addition CSS for the determination of the line width also to define the font size and line height.
- Font-size: 2em; ( to German: Font size 2em ) doubled the font size.
- Line-height: 1.2em; ( in German: line spacing 1.2 em) sets the line spacing to 120 % of the font size. Between the lines, that is, 20 % of the font size will be released as a bullet.