I stumbled across this post on Thingiverse today. It is a program that helps you track the amount of filament left on your spool! You enter in the initial data (weight, approximate length, color, type, etc.) and then you enter each project for that spool each time you print. The program then gives you the amount left in actual length and percentage. Of course, no program can tell you how much you actually have, but it should be a rough estimate.
For us, this is a must-have, as most of our prints are 8+ hours and 30+ meters of material. We are talking a day of production and wasted material if we run out mid-print. That is huge.
Hope you find this helpful!