What is EPI?
EPI stands for Ends Per Inch. Some weavers use WEPI, which is the same, just Warp Ends Per Inch. 10 EPI means there are 10 ends per inch of weaving. While 12 EPI (finer warp) means there are 12 ends per inch of your weaving. You will need MORE warp when using size 12 EPI.

This will hopefully start to make sense in a moment.

Calculating how much warp you need for a project.

Let’s say my project is a 6 inch wide medicine bag. I want the length of the weaving, including fringe to be 12 inches long. Now, I’m using 10 EPI sized warp. That means I’ll need ten ends per inch of weaving. We take these numbers and multiply them together, 6x12x10=720 total inches needed.
Now we convert to yards by dividing by 36 (as that’s how the balls of warp are measured/sold).
So, 720/36=20 that is 20 yards needed for my bag.

Start by figuring these three numbers:
1) Measure the length of your desired project (24-30 inch headband or apron, 4-6 inch bag, 60 inch robe, etc)
2) Figure an estimate on how long/tall your weaving plus fringe will be (the desired vertical/hanging length of your weaving)
3) Decide whether you’re using 10 EPI or 12 EPI.
Now MULTIPLY numbers 1, 2, and 3. This is your INCHES SUBTOTAL, the total inches of warp you need.
The final step, you need to convert to yards!
Divide your INCHES SUBTOTAL by 36 to find how many TOTAL YARDS you’ll need for your project.

Remember which size EPI you used in your figuring, and order the correct amount.