When I had my weaving lesson last week my teacher gave me a weaving planning sheet.
The sheet takes you through all the calculations you will need to determine how much yarn you will need for a given project. For the warp (vertical yarns) you start with the desired dimensions of your finished cloth, add in extra for take-up and shrinkage, then calculate how much yarn you need based on ends per inch (epi, this is the weaver’s term for how many strands of yarn are in an inch of warp) and the length of your cloth. The process is very similar for the weft (horizontal yarns). The main difference is that the number of ends per inch is predetermined for your warp by the heddle you use (The heddle is the plastic thing in back of the loom that you thread all the warp yarns through. You can buy heddles that have more or fewer ends per inch to weave a coarser or finer cloth.), but the number of picks per inch (ppi, this is the weaver’s term for how many times the yarn crosses the warp in an inch) is determined by how closely you beat your weft.
So for a “balanced weave” I would have 8 strands going vertically and 8 strands going horizontally. But if I beat my weft closer I could end up with 8 strands going vertically and 9 or 12 (or any other number) strands going horizontally. This also goes the other way. I could have fewer weft (horizontal) yarns than warp (vertical) yarns.
So why does this matter?
The more closely packed your weft yarns are, the more yarn you will use. So if you are really close on yarn it is a good idea to do a few inches as a sample just to make sure you will have enough.
The picture you see above is my planning sheet for a plaid project bag. I want the finished bag to be an 8″ by 8″ cube with a fold-over top. I planned for the front, bottom, back, and flap to be all one piece, then for the 2 sides I skip an inch or so and start weaving the next pieces. My EPI (ends per inch on the warp) is 8 and my PPI (picks per inch on the weft) is 12. But my original calculations assumed a balanced weave. I started the project with almost twice the yarn my calculations said I needed, so even though my math was way off I went ahead with the project.
I guess it’s a good thing I paid attention in Algebra!
Do you have a process for calculating yardage for your weaving? Let’s talk about it in the comments.