multicols package set column width

Question

Iam having trouble making my text evenly distribute over the entire width of the page

\oddsidemargin -0.3in
\evensidemargin -0.3in
\textwidth 7.3in
\textheight 9in

\begin{multicols}{2}

my text

\end{multicols}

my right side margin is larger than left margin.

Answer 1

\oddsidemargin is used on odd numbered pages and \evensidemargin is used on even numbered pages; neither of those is directly setting the right margin. To center your text with a \textwidth equal to 7.3 inches on paper that's 8.5inches wide, you should use

\setlength{\oddsidemargin}{-0.4in}
\setlength{\evensidemargin}{-0.4in}
\setlength{\textwidth}{7.3in}

That sets the left margin to be 1 inch minus 0.4 inches, which is 0.6 inches. That 0.6 inches plus 7.3 inches for text leaves you a right margin of 0.6 inches.

Answer 2

Margins are best managed with geometry

\usepackage{geometry}
\geometry{letterpaper,textwidth=7.3in,hmarginratio=1:1,
  textheight=9in,vmarginratio=1:1,heightrounded}