baselineskip for 10pt, 11pt and 12pt fonts

Question

There looks like a mismatch between font height and baselineskip:
10pt - 12.0pt (12.0pt)
11pt - 13.6pt (13.2pt)
12pt - 14.5pt (14.4pt)

For example, if font height is 12pt, then baselineskip should be 12 * 1.2 = 14.4pt, but it is actually 14.5pt. I haven't figured out why it is defined like this. Only the value for 10pt font height is exact. I think this is why we need setstretch{1.213} but not setstretch{1.25} for a one-half spacing using 11pt font.
The question is, where are these baselineskip values defined and why they mismatch 1.2 * font height for 11pt and 12pt fonts?

David Carlisle · Answer

The baselines are not calculated they are set, note also the fontsize at 11pt option is not 11pt but 10.95pt.
So looking at the standard article class 12pt is used for large in the default 10pt option and for normalsize in the 12pt option, but with different baselineskip. the sizes are defined for the standard classes in the files size10.clo, size11.clo, size12.clo
The 12pt definitions are:
size10.clo:
DeclareRobustCommandlarge{@setfontsizelarge@xiipt{14}}

12pt on 14pt
size11.clo:
has the same definition of large as the default option.
size12.clo:
   @setfontsizenormalsize@xiipt{14.5}%

12pt on 14.5pt
Note these are just arbitrary sizes chosen by Leslie Lamport at the beginning of time and copied with slightly modified code but the same values into LaTeX2e. There is no fixed relationship between font size and baselineskip.

baselineskip for 10pt, 11pt and 12pt fonts

One Answer

Add your own answers!

Ask a Question