I have a number of lines that came with reels I collected...don't know the weights so I tried basically the method outlined by vicryder.

I have a digital scale...happens to measure in grams oz and lb's...laid a small rod on the scale to Tare it and after coiling 30ft on my fingers...about 4" coils...laid on the scale platform and held it in place with the rod which had already been accounted for...as mentioned the line sticking out is easily supported ...in fact I could manipulate it and find the weightless sweet spot...14 grams= 216 gr= 8wt.

I point this out because I find it easier to do than use the Umqua scale and you can pick up these scales at Harbor Freight very reasonably especially when on a coupon.