Calculating 'dead volume' of my filastruder

Hello,
I am currently extruding PCL but soon working with other, more expensive, polymers that are of concern. In order to get correct dead volume calculations is the best way to weigh the material in prior and then weigh the filament material again post extrusion? Then with those two numbers, would I be able to calculate the percent loss by the difference of the two weights divided by the original weight of the material in? Anyone with pointers or prior experience with this please give me your opinion thank you.