Running out of space on /usr or just want to slim down your system? In Arch (or any distro using pacman as their package manager), you could just use “pacman -Qi” and parse the output. But that does not really tell you the “actual” amount of space required for a package. e.g. on my system skype is the only package using qt so having skype installed costs me at least 105Mb (~20Mb for skype and ~85Mb for qt).
I try to address this with a python script called bigpkg. It works by calculating the size of a package as its actual size plus the sum of its share of its dependencies (for each dependency, add the dep size divided by the number of packages needing that dep).
This was the output of the top 10 packages on my system:
It is not perfect (e.g. jabref is one of two packages on my system using openjdk6 so removing it will not save 83MB as the ~75MB of openjdk attributed to it is still needed by the other package.) But gives a fair indication of what is taking up your hard-drive space.