{"rowid": 330, "title": "An Explanation of Ems", "contents": "Ems are so-called because they are thought to approximate the size of an uppercase letter M (and so are pronounced emm), although 1em is actually significantly larger than this. The typographer Robert Bringhurst describes the em thus:\n\n\n\tThe em is a sliding measure. One em is a distance equal to the type size. In 6 point type, an em is 6 points; in 12 point type an em is 12 points and in 60 point type an em is 60 points. Thus a one em space is proportionately the same in any size.\n\n\nTo illustrate this principle in terms of CSS, consider these styles:\n\n#box1 {\n     font-size: 12px;\n     width: 1em;\n     height: 1em;\n     border:1px solid black;\n}\n\n#box2 {\n     font-size: 60px;\n     width: 1em;\n     height: 1em;\n     border: 1px solid black;\n}\n\nThese styles will render like:\n\n M\n\nand\n\n M\n\nNote that both boxes have a height and width of 1em but because they have different font sizes, one box is bigger than the other. Box 1 has a font-size of 12px so its width and height is also 12px; similarly the text of box 2 is set to 60px and so its width and height are also 60px.", "year": "2005", "author": "Richard Rutter", "author_slug": "richardrutter", "published": "2005-12-02T00:00:00+00:00", "url": "https://24ways.org/2005/an-explanation-of-ems/", "topic": "design"}