How to use the weaving warp calculator
- Enter the width in the reed in inches and the ends per inch.
- Pick a length unit and enter the finished woven length, plus the loom waste per end in the same unit.
- Open More options to add take-up and shrinkage, extra edge ends, and the yards in a skein.
- Read the number of ends, the length of each end and the total yards of warp yarn.
Formula
ends = width x ends per inch + edge ends, rounded up
length per end = woven length x (1 + take-up / 100) + loom waste
total yarn = ends x length per end
Each warp end runs the full length of the piece plus the waste at both ends, so total yarn is the number of ends times that length. Lengths are converted to inches internally and shown in yards.
20 inches at 10 ends per inch
Twenty inches at 10 ends per inch is 200 ends. With 3 yards of woven length and 1 yard of waste, each end is 4 yards, so the warp is 200 x 4 = 800 yards, or about 731.5 meters.
With 10 percent take-up, each end is 3 x 1.1 + 1 = 4.3 yards and the warp is 860 yards. Adding 4 extra edge ends makes 204 ends and 877.2 yards. If skeins hold 230 yards, 800 yards takes 4 skeins.
Ends, sett and waste
The ends per inch, called the sett, depends on the yarn and the weave. A tight sett makes a firm cloth and a loose one a soft cloth, so use the sett that suits your yarn and project. This page then counts the threads for the width you choose.
Loom waste is the length you cannot weave, such as the length used for tying on and the fringe, and it differs between looms. Take-up is the extra length the yarn needs because it bends over and under the weft, and shrinkage is what the cloth loses when washed. Test with a sample to find your own numbers.
Other yarn tools
The weft is a separate amount, so see the Yarn Yardage Calculator. Plan sewn projects with the Fabric Yardage Calculator, and work out knitting gauge with the Knitting Gauge Calculator.
Assumptions and limits
- Every end is the same length and the sett is the same across the width.
- The loom waste is per end and in the same unit as the length.
- The weft yarn is not included.
- Extra edge ends are added to the width count.
Frequently asked questions
How many warp ends do I need?
Multiply the width by the ends per inch. A 20 inch width at 10 ends per inch needs 200 ends, and the page rounds up if the result is not a whole number.
How much warp yarn do I need?
Multiply the number of ends by the length of each end, which is the woven length plus take-up and loom waste. 200 ends of 4 yards each is 800 yards.
What is loom waste?
It is the warp length you cannot weave, mostly the part used to tie on and the fringe. It differs between looms, so measure yours.
What does take-up mean?
It is the extra warp length used because the threads bend over and under the weft. Enter it as a percent in More options.