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What is the length of one PT in Tex?
For most other software, 1 pt is 1/72 in, which is 0.352777778 mm. Also called Postscript Point, in TeX this is called a big point (bp). ex and em are not a fixed length, as they depend on the fontsize.
What are the denominators for 1em and 1ex?
Actually the two approximations, given with 20 places after the decimal mark, for 1em and 1ex, are exact, the denominators are powers of 2, the complete decimal expansion only has zeros after those shown. I still do not quite understand why 1em turns out to be 655361sp and not 655360sp=10pt in the case of the CM font. This 10pt+1sp is strange.
How big is an inch in TeX format?
21 An inch is 25.4 mm. For TeX, 1 pt is 1/72.27 in, which is 0.351459804 mm. For most other software, 1 pt is 1/72 in, which is 0.352777778 mm. Also called Postscript Point, in TeX this is called a big point (bp). ex and em are not a fixed length, as they depend on the fontsize. (See this question.)
How big is 21 an inch in Tex?
21 An inch is 25.4 mm. For TeX, 1 pt is 1/72.27 in, which is 0.351459804 mm. For most other software, 1 pt is 1/72 in, which is 0.352777778 mm. ex and em are not a fixed length, as they depend on the fontsize.
How are SP units converted to internal dimensions?
The underlying thing is that internally all dimensions are integer multiples of sp unit, hence there must be some conversion done. A few salient points: the set of those internal dimensions obtainable from a specification in cm has non empty symmetric difference with the set of those dimensions obtainable from a dimension with in as unit.
What are the possible dimensions / sizes / units?
As some commands, such as \\hspace understand all of them, I would like to have a reference or complete list of possible dimensions or sizes including a description of what they mean. mu: math unit, 1 em = 18 mu, where em is taken from the math symbols family, various lengths are derived from it ( thinspace, thickspace, etc.)
How to convert 1pt to mm in Tex?
Here is a variant on Herbert’s answer, using \\dimexpr instead (inspired from the thread \\ifnum for real numbers of comp.text.tex), which allows to do conversions in a purely expandable way. The syntax is \\convertto {mm} {1pt} to convert 1pt in mm: