\settoheight

Synopsis:

\settoheight{len}{text}

Sets the length len to the height of box that LaTeX gets on typesetting the text argument. The length name len must begin with a backslash, \.

This will show how high the characters go.

\newlength{\alphabetheight}
\settoheight{\alphabetheight}{abcdefghijklmnopqrstuvwxyz}
\the\alphabetheight

If no such length len has been declared with \newlength, if for example you mistype as \settoheight{\aplhabetheight}{abc...}, then you get something like ‘Undefined control sequence. <argument> \alphabetheight’. If you leave the backslash out of len, as in \settoheight{alphabetheight}{...} then you get something like ‘Missing number, treated as zero. <to be read again> \setbox’.