“Take a look at your stash. See all those leftovers from projects past? Assorted oddballs and mini-skeins of this and that? What if you wanted to use them for a project? Some are still in the original packaging, but many have already been wound into balls and partly used. How on earth do you figure out how many yards they actually have?”
I actually did this not too long ago while working on a project! I thought I was being very ingenious . . .
To read the entire article: Knitting Needles and Tools Reviewed.
And here is a link to a page full of how-to’s as well!