There are a number of utilities that create .zip files. Their efficiency is
a function of the compression engine they use and I would expect that PKzip,
WinZip, 7Zip and others use their own engine. Therefore if there is a single
stand alone utility that provides this information it would need to be aware
of all the zip tools and the compression algorithms and update they have
used over the years. Alternatively they most likely do a simple calculation
of the compressed size to the uncompress file size to determine a 'Ratio'.
I know than WinZip ands most likely others will display the ratio on the
contents (files contained in) a zip file before you extract.
JS
