To find the WPI, you can purchase a WPI Tool Kit or you could just as easily grab a ruler or yard stick you may already have. You will also need to use either the chart from last weeks blog or "The Knitter's Handy Guide to Yarn Requirements", available at Chix with Stix, and the yarn in question. All you need to do is take your yarn, wrap it around the ruler/tool until you have covered one full inch; making sure not to wind too tightly/loosely, overlap your yarn or have gaps between the wraps. Now count how many times the yarn wrapped around the ruler within that inch and match the number to the WPI portion of the chart. Now you will know the weight of your mystery yarn!
See how simple that was?!? Take a little time and go through your stash and find the weights of your mystery yarns!