Loom Warp Length Calculator
Planning a warp means knowing how many threads (ends) to wind and how long each must be once you allow for loom waste, take-up and shrinkage. Enter your finished cloth width and length, the warp sett, edge ends, take-up percentage and loom waste, and this tool returns the number of ends, the warp length per end and the total warp yarn to wind.
Warp length formula
Number of ends = round(finished width * sett) + edge ends
Warp length per end = finished length * (1 + take-up / 100) + loom waste
Total warp (inches) = warp length per end * number of ends
Total warp (yards) = total inches / 36
Take-up lengthens each warp end to allow for interlacing and shrinkage; loom waste adds the fixed unweavable length once per end.
Worked example
A 20 inch wide cloth at 12 EPI needs 20 times 12 = 240 ends, plus 4 edge ends = 244 ends. For a 60 inch finished length at 10 percent take-up plus 27 inches loom waste, warp length per end = 60 times 1.10 plus 27 = 93.00 inches. Total warp = 93 times 244 = 22,692 inches, or 22,692 / 36 = 630.33 yards.
Loom warp length: frequently asked questions
How do you calculate the number of warp ends?
Multiply the finished width by the warp sett (ends per inch, EPI), then add edge ends if you use a floating selvage or doubled edges. Number of ends equals width times sett, plus any extra edge ends.
What is loom waste and take-up?
Loom waste is the unweavable warp tied to the front and back beams (often a fixed length per project). Take-up and shrinkage are the percentage the warp shortens as it interlaces and is washed. Both must be added to the finished length so the woven piece comes out the right size.
How much total warp yarn do I need?
Multiply the warp length per end (finished length plus take-up plus loom waste) by the number of ends. That total length of yarn is what you wind on the warping board, usually quoted in yards or metres.
Why add a take-up percentage?
As warp threads weave over and under the weft they follow a longer, wavy path, and the cloth shrinks when washed. A take-up and shrinkage allowance (commonly around 10 percent, but test your draft and fibre) keeps the finished length accurate.
Sources and notes
- The calculation is standard weaving warp planning: ends equal width times sett, and per-end length equals finished length plus take-up plus loom waste.
- Sett, take-up and loom waste are your project and loom values; this tool assumes no fixed figures.
Reviewed by the CalculatorHub team, edited by James Graham, 19 June 2026. See our methodology.