i was just about to post this same question. i know how to substitue when i have the yarn in hand, but i'm really confused on knowing what yarn i can sub in, and how much of it i need. do you just need to choose the same weight and then get the same yardage? if it's the same weight it SHOULD be the same length right? when they do sweater patterns, do they leave a buffer so you have enough? i don't need to buy an extra ball just to be safe do i?
i want to order yarn off knit picks for my next sweater, but i'm dragging my feet because i'm scared i won't get it right!
i always used my lys when i bought subs before, but i can't afford the prices now...that and the last time i went to buy sock yarn there, the person helping me confused me SO much because she was trying to convert mesurements and stuff over from a foreign yarn band, and i was completely lost! i'm very visual, so having someone explain it to me by doing math in their head just makes matters worse.
is there a website or book that explains it well?