I can't believe I'm asking this, I'm sure it is the most obvious thing in the world (and I searched, and I couldn't find an answer...)

but - how do you know how much yarn you have left when you've used up part of a skein? I could try to guesstimate, "half a skein" or something, but that's harder when you pull out of the middle. The skein collapses, so the size is much different than when you started.
I'm a new knitter, but bits of different yarns are starting to pile up. I'd like to use them, but...no can do if I don't know how much I have!
I am *not* feeling like a smart blissknits right now.
