Weaving Warp Calculator (Ends, Sett, Warp Length with Take-Up & Loom Waste, Weft Yardage)
Plan a weaving project: warp ends from width and sett, total warp length with take-up, shrinkage, fringe, sampling and loom waste, the yards or metres of warp and weft yarn, skeins to buy and the heddles per shaft — for rigid heddle and floor looms.
How it works
ends = width in reed (in) × sett (+2 floating selvedges); width in reed = finished width ÷ [(1 − 0.6 × take-up) × (1 − shrinkage)] · warp length = Σ pieces [finished ÷ ((1 − take-up)(1 − shrinkage)) + 2 × fringe] + loom waste + sampling · warp yards = ends × length; weft yards ≈ picks × width in reed × 1.1
Every weaving project starts with the warp calculation, and every weaver has cut a warp short once. Working backwards from the finished cloth: it will shrink in the wash, it was shorter under tension than it looks (take-up), each piece needs fringe at both ends, the loom cannot weave the last stretch (loom waste), and you should sample. The width does the same in the other direction, which sets how many ends to wind at your sett. From ends and length come the yards of warp yarn, and from picks per inch the weft — the two numbers that tell you how many cones to buy.
Worked example
Two 25 × 180 cm scarves at 12 epi with 10 cm fringes: 180 cm finished becomes 217 cm woven after 8% shrinkage and 10% take-up, 237 cm with fringe, 474 cm for two, and 5.54 m of warp with 60 cm loom waste and a 20 cm sample. The 25 cm scarf is sleyed at 28.9 cm, so 137 ends (with floating selvedges 139) — about 830 yards of warp and about 750 yards of weft at 12 ppi: four 220-yard skeins of each.
Frequently asked questions
How do I choose the sett?
Wrap the yarn around a ruler with the wraps just touching and count wraps per inch. For plain weave use about half the WPI; for twill about two-thirds; for a drapey scarf go a little more open, for placemats or bags tighter. Weave a sample — the sett that looks right on the loom often needs a change after washing.
What is take-up and how much should I allow?
The warp bends over and under the weft, so a metre of warp weaves less than a metre of cloth; plain weave with a weft of similar size takes up about 10%, twills less, thick weft on fine warp more. It is separate from washing shrinkage, which is another 5–15% depending on fibre.
How much loom waste?
The length from the front tie-on to the back apron rod that cannot be woven: 45–60 cm on rigid heddle and table looms, 60–90 cm on floor looms. Tying on to a dummy warp or using a lashing method reduces it, and putting several pieces on one warp spreads it.
Related calculators
Fibre-craft estimates depend on your tension, yarn, stitch pattern and blocking. Always knit or crochet a gauge swatch, wash and block it as you will the finished piece, and measure from that.