Fabric Pilling Calculator

The calculator separates how easily a fiber sheds loose ends (base pilling propensity) from how strongly it holds onto the pills those ends form (retention factor). Polyester and acrylic have high values on both: they shed ends readily and their strong filaments keep the resulting pill anchored to the fabric surface, while a cotton pill of the same size snaps off and falls away because cotton fiber is comparatively weak — so the visibly pilled fabric is often the more durable fiber, not the weaker one.

The wear-progression factor is modeled as a logarithmic curve, scaled so it reaches its maximum around 100 wears — that mirrors how pilling actually develops: loose fiber ends work free and tangle fastest early on, and once most of the surface's available loose ends have already balled up or broken off, additional wear adds comparatively little new pilling. This is why the calculator asks for 'wears before assessment' rather than assuming pilling keeps getting linearly worse forever.

It depends on the fiber, which is exactly what the shaver-effectiveness output tracks. High-retention fibers like polyester or nylon respond well to shaving because their pills stay firmly attached and are easy for the blades to catch; low-retention fibers like cotton or silk often shed pills on their own before you'd even get to shaving them, so the calculator estimates less improvement available from that specific tool.

It's the 1-5 surface-appearance grading scale defined by ISO 12945-2, the international standard for the modified Martindale pilling method: a fabric sample is abraded against a standard wool worsted cloth for a set number of rubs on a Martindale tester, then an assessor compares its surface to standard grading photographs and assigns a grade from 5 (no visible change) down to 1 (very severe pilling). This calculator's martindaleRating output is modeled on that same 1-5 scale, translated from the fiber, twist, density, care, and wear inputs you enter rather than from an actual abrasion test.

In this model both are true reduction factors, not delays — twist and density directly scale down the effective severity score by locking fiber ends in place (high twist) or leaving them less room to migrate to the surface (dense weave), which lowers both the peak pilling severity and pushes out the estimated wears-until-noticeable figure. They don't change the fiber's underlying base propensity, though, so a loosely twisted acrylic yarn will still out-pill a tightly twisted one even at the same density.