How to Calculate Warp & Weft

Weaving on a traditional loom is a favorite hobby of crafters.

Weaving is a skill that has existed for many centuries; it involves the careful assembly of yarns, twills and cottons through a device known as a loom that produces beautiful garments and household articles, such as shawls, blankets, table runners and scarves. Novice and experienced weavers sometimes learn by trial and error the amount of material needed to perform the craft. Loose threads assembled on a loom from top to bottom are known as the warp, and the cross threads horizontally woven in between them are called weft. Weaving projects begin with a selection of the project, determination of the fabric, reed choice and calculation of the warp and weft.

Things You'll Need

• loom

Instructions

1. Select the project. Pick a project and determine the approximate size of the object, considering the hem and shrinkage. For example; if the project is a baby blanket projected to have a width of 36 inches and length of 36 inches with a 2-inch hem, the blanked is 40 inches. Add 10 to 15 percent for shrinkage, which equals another 6 inches and a total project length of 46 inches.

2. Determine the take-up and add additional length for loom waste. Add an additional 10 percent of the final width for take-up and 10 percent for loom waste, rounding both up to 46 inches plus 10 inches. Multiply the full length by 2 to make more than one object, and add the loom waste: 46 x 2 = 92 + 10 = 102.

3. Calculate the warp. Determine the amount of yarn needed by adding take-up and shrinkage of 10 percent each to the final planned width (loom width). For example; for a width of 12 inches plus 1.2 inches for take-up plus 1.2 inches shrinkage equals a width on the loom of 14.4, or 15 inches multiplied by the ends per inch (epi) of 15 yields warp ends 225. Subtract 2 to adjust for pattern for a total number of warp ends to wind of 223 yards. Multiply the total ends to wind by the length of each warp thread (in yards) to determine the amount of yard needed: 223 x 4.3 = 960 yards.

4. Determine the amount of yarn needed for weft. Multiply the width on the loom times the beat (shots per inch) times warp length for weaving to determine the weft needed; divide the resultant by 36 to determine the yards. For example; 15 x 15 x 130 = 29, 250 inches / 30 = 813 yards of weft needed.

References

• Weaving Today; Learn how to weave with weaving today: Weaving terms, warping a loom and more; 2011
• Weavespindye; Right from the start; Weavespindye; 2011