Convert from em to point [Didot]

Unit Definition (em)
The em is a printer's unit of relative distance. One em is the height of the type size (in points) being used. If 12 point type is being set, then one em is 12 points, and so on.

Unit Definition (point [Didot])
The point is a unit of length used by typographers and printers. When printing was done from hand-set metal type, one point represented the smallest element of type that could be handled, roughly 1/64 inch. Eventually, the point was standardized in Britain and America as exactly 1/72.27 = 0.013 837 inch, which is about 0.35 mm (351.46 micrometers). In continental Europe, typographers traditionally used a slightly larger point of 0.014 83 inch (about 1/72 pouce, 0.377 mm, or roughly 1/67 English inch), called a Didot point after the French typographer Firmin Didot (1764-1836). In the U.S., Adobe software defines the point to be exactly 1/72 inch (0.013 888 9 inch or 0.352 777 8 millimeters), a unit sometimes called the big point (bp). The German standards agency DIN has proposed that all these units be replaced by multiples of 0.25 millimeters (1/101.6 inch).