By Amy King
In the last issue I explained the basics of weaving with rigid heddle looms. Now for the fun part: planning your projects! Don’t let this step intimidate you. Figuring out a weaving project is fairly simple when you have a formula to work with. Fill out the charts below and you’ll be happily on your way to a new design. Let’s start with a simple scarf.
Step 1. Find your WPI (wraps per inch) and decide whether or not you want a balanced weave (more on that here). For this exercise we're going to assume you want a balanced weave and are using a standard sock yarn.
WPI with yarn.
Let’s assume our the WPI for our yarn is 20. Twenty divided by two is 10, so you’ll need a 10 dent reed/heddle for a balanced weave. If your yarn doesn't have a WPI that divides evenly you’ll have to use subjective reasoning. If it's 10.5, I use a 10; if it's 11, make a judgment call based on how you want the finished fabric to appear. A 10dent reed would create a looser weave; a 12dent will be tighter.
To help you in the decision, consider how your yarn behaves. If it tends to puff a lot like a Targhee sheep’s wool then you might want to choose the smaller dent knowing any spaces will definitely fill in. If you're using a cotton that will just stay where it’s put; a larger dent would be suitable.
If you're embarking on a large project or using a pricey yarn, follow knitting’s golden rule and make a swatch. If you are making a simple scarf it's much less of a gamble to just push ahead with whatever your gut tells you.
Step 2. Figure out how much yarn you need. Fill in the information on the handy little chart below to determine the needed yardage.
Warp Calculation
Desired finished length of the piece (A) 
inches 
Length of fringe or turnup length (B) 
inches 
Total 1 (A + B) 
inches 
Total number of pieces used in the project 

Total 2 (number of pieces x Total 1) 
inches 
Loom waste 

10% shrinkage 
inches 
10% takeup 
inches 
Total length (Total 2 + waste, shinkage, and takeup) 
inches 
Width of piece 
inches 
Shrinkage 10% 
inches 
Drawin (plan for 12 inches) 
inch 
Total width 
inches 
EPI (8dent, 10dent, etc) 

Ends : (= total width x EPI) 
inches 
Total 3 (Ends x total length) 
inches 
Convert Total 3 to yards (Total 3 x 36) 
yards 
Weft Calculation.
If you're doing a balanced weave you can plan on using the same amount of yarn, less the fringes and yarn waste. The more accurate way is to do a swatch then use this chart:
A = Pics per inch 
/inch 
B = Number of inches needed 
inches 
C= A multiplied by B 
inches 
D=10% margin of error 
inches 
C + D is your total 
inches 
Change your total to yardage 
yards 
You can also reverse engineer this design. This chart above helps you plan a project by the size you want the project to be, the one below will help you figure out what you can make with the yarn you have on hand.
Number of yards total 
yards 
Divide in half Half is for the weft – half is for the warp 
yards 
Convert to feet 
feet 
Length of item wanted 
feet 
Waste of tie ones and take up 
feet 
Add length and waste together 
feet 
Amt of yarn divided by length needed ** This is the number of ends you will have to warp 
ends 
Divide by 2 
slots 
Round down to whole numbers.
My yarn is Opal Sock yarn 464 yards per ball and I wanted a 6foot scarf. This is how my chart would look for that.:
Number of yards total 
464 yards 
Divide in half Half is for the weft – half is for the warp 
232 yards 
Convert to feet 
696 feet 
Length of item wanted 
6 feet 
Waste of tie ones and take up 
1.5 feet 
Add length and waste together 
7.5 feet 
Amt of yarn divided by length needed This is the number of ends you will have to warp 
92 ends 
Divide by 2 
46 slots 
At this point we can measure out the distance between our loom back beam and the warping peg to set up our loom with 46 looped ends pulled through the slots. When we do the final set up, cutting out looped ends, winding on to the back beam and finishing off dressing the heddle with one end (out of the two there) from each slot into a heddle hole, we'll have 92 ends.
These charts may seem a little lengthy, but much like a knitted garment calculator, once you get into inserting numbers and seeing how they work on your loom, they start to make more sense. There are patterns and kits available to make rigid heddle items but if you can set up your own, you'll find that you have much more versatility in weaving.
Once you master the simple patterns and straightforward plain or tabby weaving, it will be easier to get going on more complicated sets and changing up your colors or changing the balance of the fabric. We’ll talk about that next time.