Aprondress Calculations

Measuring the sample before and after finishing gives me the rest of the data I need to calculate how much yarn I need to buy.  The Handweavers Guild of America has has a great article on how to calculate this, which I’ve drawn from below.

Calculating the Warp

First, the calculations for take-up and shrinkage:

Width Length
On the loom 8″ 8.25″
Off the loom 6.75″ 7.5″
Take-up 15% 10%
After finishing 5.75″ 6.5″
Shrinkage 15% 13%

Next, determining how many warp ends I need:

Final planned width (“) 20″
+ Take-up (15%) + 3″
+ Shrinkage (15%) + 3″
= Width on the Loom = 26″
x epi (ends per inch) x 15
= Warp Ends =  390 ends
+/- Adjustment for pattern +2 (add balance threads)
= Total Ends to Wind = 392

Then I need to determine the length of each end:

Final length (6 yards) 216″
+ Shrinkage (13%) 28.08″
+ Take-up (10%) 21.6″
+ Loom waste 36″
= Total warp length (rounded up) 302″

This gives us the amount of yarn needed for the warp:

Total Ends To Wind 392
x Length of each warp thread x 302″
= Total warp needed (rounded up) = 3289 yards

Calculating the Weft

This is a much simpler calculation.  Since I’m only doing a few decorative stripes of red (say, 12″ maximum), I will calculate as if the whole thing was orange.

Width on the Loom (“) 26″
x Beat (shots/inch) x 15 shots/inch
x Warp length for weaving (“) x 302″
= Total weft needed in yards (rounded up) = 3272 yards

The Final Totals

I need 3289 yards of yellow wool, which rounds up to 15 balls of yarn.
I need 3272 yards of orange wool, which rounds up to 15 balls of yarn.
Plus 2 balls of red wool for decorative stripes.

At $3.39 a ball for yellow/red, and $3.59 a ball for the orange, my total cost for the yarn will be $111.48 US, plus tax/shipping.  That boils down to $18.58 a yard (after finishing).

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