How Much Yarn a Weaving Project Needs

Running out of yarn mid-warp is one of the most avoidable mistakes in handweaving, yet it happens constantly. This article gives you a reliable method to calculate exactly how much warp and weft yarn a project needs before you wind a single thread. You will learn the formula, the fudge factors that matter, and how to read the sett and width figures in a pattern book so your numbers are trustworthy.

Why yarn calculations go wrong

Most shortages come from ignoring three hidden costs: loom waste, take-up, and shrinkage. The cloth you see on paper is always longer and wider than the cloth that comes off the loom. If you calculate only the finished dimensions, you will come up short every time.

Loom waste

This is the warp you cannot weave: the length tied to the front and back aprons, plus the unwoven ends between the last pick and the knots. On a typical floor loom, budget 60 to 90 cm (24 to 36 inches). Table looms and rigid heddle looms often waste less; large countermarch looms waste more. Measure your own loom once and reuse that number.

Take-up and shrinkage

Take-up is the length lost as warp threads bend over and under the weft. Shrinkage happens during wet finishing. Together they commonly remove 10 to 15 percent from both length and width. For highly textured or heavily fulled wool, plan for more.

The core calculation

Work in two parts: warp first, then weft.

Step 1: Total warp ends

Multiply your sett (ends per inch, or EPI) by the warp width in the reed. If your pattern book calls for 24 EPI and you want cloth 20 inches wide in the reed, that is 24 x 20 = 480 ends.

Step 2: Warp length per end

Add together the finished length you want, take-up and shrinkage allowance, and loom waste. Example: 2 metres finished + 0.3 m for take-up and shrinkage + 0.75 m loom waste = 3.05 m per end.

Step 3: Total warp yarn

Multiply ends by length: 480 x 3.05 m = 1,464 m of warp yarn.

Step 4: Weft yarn

Weft is often close to warp when picks per inch (PPI) roughly equals EPI in a balanced weave. Estimate weft length as picks per inch x woven length in inches x width in inches. Then convert to your yarn’s units. When in doubt, assume weft equals warp for a balanced plain weave, and add 10 percent.

Turning length into grams or yards you can buy

Yarn is sold by weight, but calculations are in length. Bridge the two using the yarn’s grist, usually printed as yards per pound (ypp) or metres per 100 g. If a yarn is 1,000 m per 100 g and you need 1,464 m of warp, that is roughly 146 g of warp yarn. Always round up and buy at least one extra unit; dye lots vary and a small margin saves a project.

A worked example

Say you want four linen placemats, each 45 x 33 cm finished, in a plain weave at 18 EPI. You decide to weave them end to end on one warp with 8 cm of loom-waste hem space between each and a fringe allowance.

• Width in reed: 33 cm plus 10 percent for draw-in and shrinkage, about 37 cm, which at 18 EPI (roughly 7 ends per cm) gives about 259 ends. Round to 260.
• Length: 4 mats x 45 cm finished = 180 cm, plus 15 percent take-up and shrinkage (27 cm), plus spacing between mats (24 cm), plus 75 cm loom waste = about 306 cm per end.
• Total warp: 260 x 3.06 m = about 796 m.

Weft in a balanced weave will be similar, so buy roughly 1,600 m total plus a safety margin.

Common mistakes and how to fix them

• Forgetting loom waste. Fix: measure your loom’s real waste once, write it on tape stuck to the castle, and always include it.
• Using finished width instead of reed width. Fix: calculate ends from the width in the reed, which is wider than the finished cloth.
• Confusing weight and length. Fix: never buy by weight until you have converted your length requirement using the yarn’s grist.
• Ignoring shrinkage on new-to-you yarn. Fix: weave and wash a small sample first, measure before and after, and use that real percentage.
• No safety margin. Fix: add 10 percent and buy a spare skein in the same dye lot.

Action checklist

• Note the sett (EPI) and reed width from your pattern.
• Calculate total ends: EPI x reed width.
• Calculate warp length per end: finished length + take-up/shrinkage + loom waste.
• Multiply ends by length for total warp.
• Estimate weft, then add 10 percent.
• Convert length to weight using yarn grist and round up.
• Weave a wash-test sample to confirm shrinkage.

Conclusion and next step

Accurate yarn estimates come down to respecting the hidden costs of waste, take-up, and shrinkage, then converting length to purchasable weight. Your next step: take your current project, run the four warp steps above, and weave one small sample to lock in your real shrinkage number before you buy.

Frequently asked questions

How much extra yarn should I buy to be safe?

Add about 10 percent to your calculated total and buy at least one spare skein from the same dye lot. This covers sampling, small errors, and repairs without leaving you stranded.

Is weft always equal to warp?

Only in a roughly balanced weave where PPI is close to EPI. Weft-faced rugs need far more weft; warp-faced bands need far more warp. Estimate weft from your actual picks per inch when the weave is not balanced.

What is a good loom-waste figure to assume?

For a typical floor loom, 60 to 90 cm is realistic. Measure your own loom once by noting the unwoven warp left after a project, and reuse that number.

Do I calculate width before or after shrinkage?

Calculate ends from the width in the reed, which is your working width plus allowance for draw-in and shrinkage. The finished, washed cloth will be narrower than the reed width.

References

• Marguerite Porter Davison, A Handweaver’s Pattern Book
• Peggy Osterkamp, Warping Your Loom & Tying On New Warps
• Handwoven magazine (Long Thread Media), project and calculation guides