fitbox2.sty

%=================================================================
% From https://tex.stackexchange.com/questions/26002/fit-text-into-given-box-by-adjusting-the-fontsize

% \RequirePackage{fp}

\RequirePackage{pbox}

\providecommand*{\DivideLengths}[2]{%
  \strip@pt\dimexpr\number\numexpr\number\dimexpr#1\relax*65536/\number\dimexpr#2\relax\relax sp\relax
}

\newsavebox{\@fbbox}
\newcommand{\fitboxratio}[4]{%
  % #1 = ratio
  % #2 = width
  % #3 = height
  % #4 = text
  \@tempdima=\dimexpr#2\relax%
  \savebox{\@fbbox}{\pbox{\paperwidth}{#4}}%
  \ifdim\wd\@fbbox=0pt\relax
    \PackageError{fitbox2}{Invalid text width 0pt for text: “#4”}
  \fi
  \typeout{FITBOX boxwidth=\the\@tempdima\space textwidth=\the\wd\@fbbox\space}%
  \edef\@hratio{\DivideLengths{\@tempdima}{\wd\@fbbox}}%
  \typeout{FITBOX boxwidth=\the\@tempdima\space textwidth=\the\wd\@fbbox\space hratio=\@hratio}%
  \@tempdima=\dimexpr#3\relax%
  \typeout{FITBOX height=\the\@tempdima}%
  \@tempdimb=\dimexpr\ht\@fbbox+\dp\@fbbox\relax%
  \edef\@vratio{\DivideLengths{\@tempdima}{\@tempdimb}}%
  \typeout{FITBOX boxheight=\the\@tempdima\space textheight=\the\@tempdimb\space ratio=\@vratio}%
  \pgfmathparse{min(\@hratio,\@vratio)}%
  \typeout{\pgfmathresult}
% \PAUSETHIS
  \csedef{#1}{\pgfmathresult}%
}

\newcommand{\fitboxmin}[2]{%
  % #1 = minimum (out)
  % #2 = list (in)
  \pgfmathparse{min(\expanded{#2})}%
  \csedef{#1}{\pgfmathresult}%
}