\documentclass[a4paper]{article}
\usepackage{bxcalc}
% Declares new units
\newcalcunit{ls}{\baselineskip}
\newcalcunit{tm}{0.05em}
%
\title{Sample document of \textsf{bxcalc}}
\author{ZR}
\date{}
\begin{document}
\maketitle

\section{Example 1}

\noindent
The quick brown fox\\[1ex-1ls]% so line skip is 1ex
jump\hspace{6tm}s\hspace{12tm}ov\hspace{2tm}er\\[1ex-1ls]
\hspace*{3tm}t\hspace{4tm}he\hspace{9tm}lazy\hspace{4tm}dog.

\section{Example 2}

\noindent
AAAAAAAAAAAAAAAAAAAA\\[\heightof{A}-1ls+2tm]
A\hspace{\widthof{A}*18}A\\[\heightof{A}-1ls+2tm]
A\hspace{\widthof{A}*18}A\\[\heightof{A}-1ls+2tm]
A\hspace{\widthof{A}*18}A\\[\heightof{A}-1ls+2tm]
AAAAAAAAAAAAAAAAAAAA

\end{document}
