Loom Width Calculator

Fabric leaves the loom wider than it ends up on your shelf, and it loses width twice on the way there — this calculator works backward through both losses to tell you how wide to actually warp. Starting from your target finished width, it first divides by (1 − shrinkage%) to find the width the fabric had right off the loom before wet-finishing pulled it in, then divides that result by (1 − draw-in%) to find the width you need on the loom itself, since weft tension pulls the selvedges inward as you weave. Applying these as sequential divisions rather than one combined percentage matters: draw-in and shrinkage compound multiplicatively against the shrinking width that remains after the first loss, so a fabric with 8% draw-in and 5% shrinkage loses about 12.6% of its original loom width overall — a shade less than simply adding the two percentages, since each loss is taken off a smaller base than the one before it.

A small selvedge allowance is added on each side for floating or doubled selvedge threads, and the total is then matched up against a list of standard commercial loom widths (10 through 60 inches) to recommend the smallest stock size that will actually accommodate the warp — useful for checking a loom purchase or confirming a project fits the loom you already own. Total warp ends is simply that on-loom width multiplied by your sett (ends per inch). The main thing to get right is realistic percentages: draw-in of 5-10% and shrinkage of roughly 5% for cotton or up to 10% for wool are reasonable starting points, but tension habits, weave structure, and fiber all shift these numbers, so a swatch test beats a guess whenever the project is worth getting exactly right.