Sometimes you need to pack a suitcase.
One way of doing it would be to have a list of how many socks, shirts etc. can the suitcase hold, then prepare these items and pack them into the suitcase. This should work, I think, but there are a few problems. First, you need to have this list ready for each suitcase. Second, well, it would be difficult to prepare such a list due to the unstable nature of clothes: wrinkling, moving, and in general the tendency of not having a steady shape.
However, the main problem with this method is that it takes a lot of time. You need to constantly check the number of items against the list, write down how many you have etc.