Posted on July 31, 2014. Filed under Tutorials, Typography. Tags: css, em, leading, line-height, measure, measurements, pica, point, relative, responsive, typography, units, webdesign. With the implementation of the em unit in CSS and it’s handy use in responsive webdesign, all of a sudden it got famous outside the typographic realm. 1. The Simple Answer An em is the same size as the font’s point