On Thu, 5 Dec 2013 12:22:48 -0800 (PST), "
wrote:

I have a standard hand-held Benzomatic propane torch, probably 35+ years
old. Fortunately I have never run out of gas in the middle of an
important project, and I do have 3 hardware stores within a five minute
drive. But I sometimes do projects late at nite after the stores would
be closed, and it would be nice to know when my propane cylinder (~2.75"
diameter, 11" long)is about to run out.
I could weigh an empty cylinder, but that could be tomorrow or late next
year, I don't have a clue how much my present cylinder has been used.
Ideas ???

JUST KEEP AN EXTRA TANK ON HAND. THEY COST LESS THAN $5. THEY DONT GO
BAD. YOUR QUESTION IS POINTLESS.....