Check a reed substitution before threading

A reed has a fixed number of dents per unit of width. Putting different numbers of ends through successive dents changes the average sett. For example, a sequence of 1, 2, and 2 ends puts five ends into three dents.

In a 12-dent reed, that sequence gives 20 EPI. It is also the worked example published by Schacht. WeaveCompass derives the sequence mathematically; it does not copy a rounded substitution chart.

Check the physical fit

Yarn must move freely through each dent. An exact average cannot tell you whether crowding will abrade the warp or create persistent reed marks. Sample the arrangement and inspect the finished result.

Know the tool’s boundary

The reed calculator searches repeats up to 32 dents and shows any remaining difference from the target. A long repeat may be mathematically close but inconvenient to thread. Prefer a manageable arrangement after inspecting the resulting sett.

This tool is for conventional reed arithmetic. Rigid-heddle holes and slots interact with the shedding system, so the same numerical substitution may not be appropriate there. It also does not validate your threading draft or required balancing ends.

If your reed uses a metric label, first use the density converter and check whether the label means dents per centimeter or per ten centimeters.

Ready to use your measurements? Open the weaving planner.