Loom Warp Length Calculator
Winding a warp too short is one of weaving's most frustrating mistakes, because there is no fixing it once it is on the loom. The warp has to be longer than the finished cloth to cover take-up as threads interlace, the loom waste tied to the beams, and any fringe. This calculator takes your woven length and width, the sett in ends per inch, and your take-up, loom waste, and fringe allowances, then computes the number of warp ends, the warp length per end, and the total warp yarn to wind. Sett and allowances come from your samples and loom, so they are your inputs.
Warp length formula
Warp ends = warp width * sett
Warp length per end = woven length * (1 + take-up / 100) + loom waste + fringe
Total yarn (in) = warp ends * warp length per end
Total yarn (yd) = total yarn in / 36
Take-up is applied to the woven length only. Loom waste and fringe are fixed lengths added once to every end. Round warp ends up to a whole number when threading.
Warping context
- Sett (ends per inch) depends on yarn and weave structure; find it from references or a sample.
- Take-up is the length lost as warp interlaces with weft, applied to the woven length.
- Loom waste is unweavable warp at the beams and is lost on every warp regardless of length.
- Fringe needs warp beyond the cloth on both ends; combine both ends in the per-end figure.
- One yard equals 36 inches; the inch is defined by the NIST Office of Weights and Measures.
Loom warp: frequently asked questions
How do I calculate warp length for weaving?
Warp length per end is the woven length you want plus take-up, loom waste, and fringe allowance. The number of warp ends is the warp width times the sett (ends per inch). Total warp yarn is ends multiplied by warp length per end. This calculator computes all three from your project figures.
What is sett, or ends per inch?
Sett, expressed as ends per inch (EPI), is how many warp threads sit in each inch of width. It depends on the yarn and weave structure and is given in weaving references or found by sampling, so it is a user input. Multiply width by sett to get the total number of warp ends.
What is take-up and why add it?
Take-up is the extra length consumed as warp threads bend over and under the weft during weaving, so the warp must be longer than the finished cloth. It is a percentage of the woven length, varying with structure and yarn. Enter the take-up percentage your sample shows; the calculator adds it.
What is loom waste?
Loom waste is the unweavable warp tied to the front and back beams plus the loom-specific allowance, lost on every warp regardless of project length. It is a fixed length you add once per end. Typical figures depend on your loom, so enter your own; the calculator adds it to every warp end.
How do I account for fringe?
Fringe on both ends of the piece needs warp length beyond the woven cloth. Enter the total fringe allowance (both ends combined) per end and the calculator includes it in the warp length. If your piece has no fringe, set it to zero.
Official sources
- NIST: Units of length (inch and yard definitions).
- NIST: Office of Weights and Measures.
Reviewed by the CalculatorHub team, edited by James Graham, 17 June 2026. See our methodology.