Sett Calculator

The multiplier reflects how much a weave structure interlaces: plain weave has every warp end going over and under its neighbor at every pick, which physically forces the ends farther apart than they sit when wrapped snugly together, hence the 0.5 multiplier. Satin/sateen floats over several picks before interlacing once, so ends barely need to separate from their wrapped density, giving it the highest multiplier at 0.75. Twill (0.667) and lace/open (0.333) sit between and below these extremes based on how much each structure's interlacement pattern forces ends apart.

When you enter a caliper-measured yarn diameter, the calculator computes a second, independent EPI estimate as (1 / diameter) × the same weave-structure multiplier × coverage factor. This doesn't average with the WPI-based recommendation — it's a separate check. If the two disagree significantly, it usually means your WPI count was off (wrap tension is easy to get inconsistent), since diameter measurement tends to be more repeatable than counting wraps.

These are fixed multipliers applied to recommendedEPI rather than independently derived: weftFacedPPI = recommendedEPI × 1.5 for fabrics like rugs or tapestry where weft dominates and needs to pack in more densely per inch than a balanced cloth, and warpFacedPPI = recommendedEPI × 0.6 for warp-dominant structures like inkle bands where fewer, more widely spaced picks let the warp show through. They aren't symmetric because weft-faced and warp-faced cloth don't require proportionally opposite pick densities.

Coverage percentage is applied as coverageFactor = desiredCoverage / 100, multiplied directly into the base sett calculated from WPI and weave structure. At the default 100%, you get the standard balanced-cloth sett; setting it below 100% (down to 20%) proportionally reduces both EPI and PPI for a deliberately open, airy weave, while raising it above 100% (up to 150%) proportionally increases them for a denser rep weave.