Often we are asked by stores to source products for them. Our latest catch is a nifty yardage counter. It's a small 2" x 2.5" gadget that clamps to a table top. You insert the yarn through a slot, secure the yarn in the slot by lifting a lever and then pull the yarn to be measured through the slot in a downward motion. It's that easy.
However, it is advisable to measure a few yards of yarn and then go back and re-measure the length with a standard tape measure or yard stick. You will then be able to adjust for the stretchiness or "give" that the yarn you are measuring has. Once you have this ratio, you can measure all the yarn you need and then adjust the final total by the "stretch ratio" obtained earlier.
It's a great way to use up bits of yarn in a stash or to insure that you have enough yarn for a project.