How much space is a line, vertically?

Question

How much space is a line, vertically ? E.g. something like "1.5em" ?

Answer 1

This would typically be measured from the baseline of one line to the baseline of another, or given by \baselineskip, and depends on the font size loaded/specified as well as the font size current active. For example, with the following \baselineskips are associated with the respective default font sizes loaded with the class:

• 10pt default font implies a 12pt \baselineskip (see size10.clo);

• 11pt default font implies a 13.6pt \baselineskip (see size11.clo);

• 12pt default font implies a 14.5pt \baselineskip (see size12.clo)

However, under a 11pt default font, \LARGE sets a font at size 17.28pt with a \baselineskip of 22pt. Conversion between lengths from points is discussed in Conversion pt to mm or cm.

You can adjust this line spacing (or \baselineskip) by making a font selection

Answer 2

\documentclass[a5paper]{article}
\usepackage{xcolor}
\def\someText{And now follows some text to
show the distance of lines. The value is saved in \texttt{\textbackslash baselineskip}.}
\begin{document}
\the\baselineskip%%% The current distance between two baselines 
\vbox to 0pt {\hbox to 0pt {\textcolor{red}{\rule[0pt]{1cm}{\baselineskip}}}} \someText

\small\the\baselineskip
\vbox to 0pt {\hbox to 0pt {\textcolor{red}{\rule[0pt]{1cm}{\baselineskip}}}}  \someText

\tiny\the\baselineskip
\vbox to 0pt {\hbox to 0pt {\textcolor{red}{\rule[0pt]{1cm}{\baselineskip}}}}  \someText

\huge\the\baselineskip
\vbox to 0pt {\hbox to 0pt {\textcolor{red}{\rule[0pt]{1cm}{\baselineskip}}}}  \someText
\end{document}