On the official site we find that:
Alien is a program that converts between the rpm, dpkg, stampede slp, and Slackware tgz file formats. If you want to use a package from another distribution than the one you have installed on your system, you can use alien to convert it to your preferred package format and install it.
The official website is here.
This tool helps us to convert packages using this:
-d, --to-deb Generate a Debian deb package (default).
-r, --to-rpm Generate a Red Hat rpm package.
--to-slp Generate a Stampede slp package.
-l, --to-lsb Generate a LSB package.
-t, --to-tgz Generate a Slackware tgz package.
We can download this tool, using git utility
$ git clone git://git.kitenet.net/alien
We can use the following commands to install it.
# perl Makefile.PL
# make install
Let’s convert one deb package to rpm.
# alien --to-rpm your-package.deb