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Calculate warp yarn requirements for loom weaving projects. Estimate total warp threads, yardage, and sett from project width and EPI.
Calculate heddles needed per shaft for loom threading. Plan heddle count from warp ends, shafts, and threading pattern for your loom.
Calculate total yarn yardage for weaving projects including warp and weft. Estimate cones needed from project dimensions and yarn weight.
Balanced plain weave uses half the wraps per inch for both warp and weft. 24 WPI yarn → 12 EPI plain weave sett.
EPI = WPI ÷ 2 (or × 0.5)Warp-faced fabrics (rep, warp satin) pack more warp threads. Higher EPI relative to WPI produces weft-hidden warp-dominant surface.
EPI = WPI × 0.6–0.8Weft-faced fabrics (tapestry, rag rugs) space warp threads widely apart so weft completely covers the warp.
EPI = WPI × 0.3–0.4Updated: July 2026
Balanced plain weave sett: 12 EPI. Twill sett: 15–18 EPI (WPI × 0.6–0.75). Sample before committing to full warp.
Weft-faced rag rug sett: 3–4 EPI. Warp spaced wide for thick weft bundles to cover completely.
Balanced twill at 24 EPI produces lightweight drapey fabric. Plain weave at 20 EPI for gauzy open cloth.
Correct sett determines fabric hand, drape, and structural integrity. Enter yarn wraps per inch (WPI) and desired weave structure to calculate recommended EPI for warp and PPI for weft using standard sett formulas.