Woven Fabric Reverse Engineering from GSM and Sett

The formula

This is the expression the tool evaluates. Every term is named underneath, with the unit it must be supplied in.

How the result is derived

Step by step, from the values you type to the figure on screen.

1. The 6 inputs are read from the form on every keystroke: Fabric GSM, Ends per Inch, Picks per Inch, Warp Crimp, Weft Crimp and Weft Count / Warp Count.
2. Each value is checked against the accepted range in the input table below. A value outside its range stops the calculation rather than producing a misleading figure — the results blank out and a message appears.
3. The validated values are substituted into the expression above, which resolves Derived Warp Count together with every supporting figure in one pass — no value is carried over from a previous entry.
4. The supporting outputs — Derived Weft Count, Warp Linear Density, Weft Linear Density, Warp Contribution, Weft Contribution, Reconstructed GSM, Warp Share of Weight, Warp Cover Factor, Weft Cover Factor and Cloth Cover Factor — come from the same pass, so they always describe the same case as the headline figure.
5. Results are rounded for display only. The full-precision value is used throughout the chain, so reading a rounded intermediate figure back into the tool by hand can shift the last digit.

What each input means

Where to read each value on the floor, the unit it must be in, and the range the tool accepts.

What the tool returns

The headline figure and every supporting value it is built from.

Worked example

The tool loads with this case already solved — the Derived Warp Count shown above is its answer. Change one value and the difference from this baseline is the sensitivity of the result to that variable.

How to use it

1. Work through the input groups in order — Measured on the Swatch and Crimp & Balance. The defaults are a realistic case, so you can change one value at a time and watch what moves.
2. There is no calculate button. Every figure recalculates as you type or drag, which is what makes this usable for a what-if sweep rather than a single answer.
3. Read Derived Warp Count in the dark results panel — that is the headline figure, expressed in Ne.
4. Check the supporting rows underneath (Derived Weft Count, Warp Linear Density, Weft Linear Density, Warp Contribution, Weft Contribution, Reconstructed GSM, Warp Share of Weight, Warp Cover Factor, Weft Cover Factor and Cloth Cover Factor) before acting on the headline — they are where an implausible input usually shows itself first.
5. Reset to defaults returns every field to the reference case, which is the quickest way to check whether a surprising result came from the tool or from an input you had changed earlier.

Where this is used

• Process planning — establishing Derived Warp Count before a trial is booked, so machine time and material in Weaving & Fabric Construction are committed against a calculated figure rather than an estimate.
• Costing and quotation — Derived Warp Count is an input to the cost sheet, and quoting from a worked number rather than a remembered one is what keeps a margin intact.
• Troubleshooting — when the floor result drifts from plan, entering the measured values (starting with Fabric GSM) shows how much of the gap in Derived Warp Count each variable explains.
• Teaching and study — the accepted ranges bracket normal Weaving & Fabric Construction practice, so moving one variable at a time shows the shape of the relationship rather than a single answer.

Assumptions and limits

• The reconstructed GSM is printed so the balance can be seen to close; it should equal the measured weight exactly, and it will, because the counts were derived from it. That is a check on the arithmetic and not on the answer. What decides the answer is the count ratio, which the mass balance cannot supply - the same weight, sett and crimp are consistent with a coarse warp and a fine weft or the reverse, and only the ratio separates them. Take it from the fabric type, from a comparable specification, or by unravelling and weighing a measured length of each in the one case where certainty is needed. Crimp is the next most sensitive input and the one most often guessed. It should be measured on threads withdrawn from the swatch and straightened under a defined tension, since guessing it wrong moves the derived counts directly, and warp and weft crimp trade against each other in a way that a single assumed pair will get wrong for any fabric not woven at ordinary tensions. The whole calculation assumes the weight is yarn: a fabric carrying a resin, a coating, a heavy softener or residual size will return counts finer than the truth, because the mass balance credits the finish to the yarn. Desize and scour before weighing where the finish is substantial.
• Every input is bounded to the range normal practice occupies (Fabric GSM 20 to 900 g/m2, Ends per Inch 10 to 400 epi and Picks per Inch 10 to 400 ppi, and so on for the rest). Those bounds are guard rails against typing errors, not a claim that the formula fails one unit outside them.
• The calculation is deterministic: the same inputs always give the same result. It carries no allowance for machine condition, operator skill, ambient conditions or lot-to-lot material variation unless an input above explicitly represents one.
• Nothing is sent anywhere. The maths runs in your browser, so the numbers you type never leave the page.

Questions people ask