Do consider using weight to estimate the remaining fabric, if the blank spool weight is consistent and you can rely on the accuracy of a new roll you should be able to measure pretty accurately with a good resolution digital scale (with more digits than a bathroom scale)
These fancy counting scales that help with the math might be overkill.
Specifically for Fabric
http://www.summitmeasurement.net/Textile...
http://www.balances.com/countingscale.ht...
I need to mantain control of how many yards I have on inventory every day. I own a small company of Custom drapes. I buy wholesale large quantities of fabric (by large I mean about 50 100 yds fabric rolls every month), it is time consuming for me to be writting down to keep record of how much yards I cut from every roll. The reason is because i suspect employees are doing jobs aside using my fabric. Is there a software I can use to create barcodes maybe so everytime someones cut fabric will have to scan barcode and substract the quantity?