UK TeX FAQ -- question label findwidth

### Finding the width of a letter, word, or phrase

Put the word in a box, and measure the width of the box. For example,

>     \newdimen\stringwidth
>     \setbox0=\hbox{hi}
>     \stringwidth=\wd0

Note that if the quantity in the `\``hbox` is a phrase, the actual measurement only approximates the width that the phrase will occupy in running text, since the inter-word glue can be adjusted in paragraph mode.

The same sort of thing is expressed in LaTeX by:

>     \newlength{\gnat}
>     \settowidth{\gnat}{\textbf{small}}

This sets the value of the length command `\gnat` to the width of "small" in bold-face text.

This question on the Web: http://www.tex.ac.uk/cgi-bin/texfaq2html?label=findwidth