Plan your weaving project with confidence

Calculate warp and weft thread counts, knot spacing, and tension adjustments for handloom weaving. Based on standard textile math, adapted for floor looms, table looms, and rigid heddle looms.

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Knot Density Calculator

Width of the finished fabric on the loom, not including selvedges.

Desired warp sett. Common range: 8-24 for balanced weave.

Wrap yarn around a ruler for one inch. Count the wraps.

For plain weave use 1. For twill or color patterns, enter the number of threads in one repeat.

Common weaving presets

Quick start with typical project parameters. Click a preset to load it into the calculator.

Saved projects

Projects you save are stored only in this browser. Click a saved project to load its values.

    No saved projects yet. Calculate and save one to see it here.

    Weaving math reference

    How the numbers work

    The calculator uses these formulas:

    • Total warp threads = fabric width × threads per inch × pattern repeat
    • Weft threads per inch = threads per inch (assuming balanced weave; adjust for weft-faced patterns)
    • Knot spacing = 1 ÷ threads per inch (distance between warp knots on the apron rod)
    • Tension adjustment = 1 + (yarn wraps per inch ÷ 100) (thicker yarn needs slightly higher tension)

    These are starting points. Always sample before warping a full project.

    Common mistakes

    • Forgetting to add extra warp for loom waste and fringe. Add 10-20% to total warp length.
    • Using the same TPI for warp and weft when the pattern is weft-faced. Reduce weft TPI by 20-30%.
    • Not accounting for yarn stretch. Elastic yarns may need lower tension.
    • Ignoring selvedges. Add 2-4 extra warp threads on each side for stability.

    Troubleshooting

    • If the fabric is too stiff, reduce TPI by 2-4 threads.
    • If the fabric is too loose, increase TPI or use a thicker weft.
    • If knots are slipping on the apron rod, use a lark's head knot and double the spacing.
    • If tension feels uneven, check that the warp beam is evenly wound.

    Example scenario

    You want a 20-inch wide scarf with a balanced plain weave. Your yarn wraps 20 times per inch. You choose 12 TPI. The calculator shows 240 warp threads, 12 weft threads per inch, knot spacing of 0.083 inches (about 1/12 inch), and a tension factor of 1.2. You would warp 240 threads, plus selvedges and waste.

    Frequently asked questions

    What is knot density in weaving?

    Knot density usually means the number of warp or weft threads per inch. It affects fabric drape, strength, and pattern visibility. This calculator uses threads per inch (TPI) as the primary density measure.

    How do I measure yarn thickness?

    Wrap the yarn around a ruler for one inch, counting the wraps. That number is wraps per inch (WPI). The calculator uses WPI to estimate yarn diameter and suggest a starting sett.

    Why does pattern repeat matter?

    A pattern repeat adds extra threads for floats or color changes. The calculator multiplies base threads by the repeat factor to give a more accurate total.

    Can I save my calculations?

    Yes. Click 'Save Project' to store the current inputs and results in your browser's local storage. You can view saved projects below the calculator and delete them anytime.