HOW I USUALLY CALCULATE AMOUNT OF WEFT YARN
My weft calculations are never accurately calculated. In fact, what I usually do is simply agree with myself that I will need the same amount of weft as warp. That gives me plenty of extra yarn in case I need it. That is because there are all the unwoven spaces on the warp, the 36" of loom waste, for example.
I have decided, however, to calculate it for these towels. If possible, I really don't want a lot of weft yarn lying around unused because I use this cotton so rarely. So here goes.
CALCULATING THE TOTAL AMOUT OF WEFT YARN
As with the warp yarns, these calculations won't be absolutely precise because I do not have the exact width of the towels on the loom. But I should be able to come close with the approximate width I came up with in the post where I discussed my warp calculations.
PPI (picks per inch) = 36 – need 5,000 yards for weft. In practice, I expect this to be quite inaccurate. I am not weaving a balanced weave structure where I would want to get the same number of picks per inch as ends per inch. I will, in reality, get fewer, if only because I am using a yarn for weft that is twice the size of the warp yarn.
36 ppi x 29" = 1,044" of weft yarn to weave 1". Again, this is an overstatement, as is clear from the preceding paragraph.
Weaving 4 towels = 166"
+ weaving 1 sample (12") = 178"
+ weaving for Crackle Study Group (36") = 214"
214" x 1,044 (amt of weft needed to weave 1" = 223,416" / 36" = 6,206 yards for weft.
My calculation for warp yarn, by the way was 7,210 yards, so I need about 1,000 yards less for the weft. But again, because I will get fewer than 36 ppi, I will need less yarn than my calculations call for.
WEFT AMOUNTS FOR EACH COLOR
But, how many colors will I need and how much of each color will I need? this is always the most difficult for me to calculate because, more often than not, I am not exactly sure just exactly how I am going to use the colors. I will probably use three colors. Assuming I would use each color equally, I would then need 2,069 yards of each color. I probably will not use them equally, so I will probably order more than I need of each color.
WHEN ACCURATE CALCULATIONS ARE NEEDED
If I were selling what I make, I could not get away with such lax calculation. I would have to know pretty exactly how much yarn I would need in order to work on setting a price. But I am not selling, so I have the luxury of not only rough-guessing but also over-estimating the amount of yarn I need.