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The customer specified the GSM. The question is what count delivers it — the calculation run backwards.
Required Warp Count
—Ne
Count that delivers the target weight at this construction
Solved Construction
Required Weft Count
—Ne
Warp Count
—tex
Warp Contribution
—g/m²
Weft Contribution
—g/m²
Warp Share of Weight
—%
Resulting Cover Factor
—K
The solved count will rarely be a commercial one — 29.9 Ne means ordering 30s and accepting the small GSM error, or adjusting pick density to compensate, and the second is usually cheaper. Crimp is an input here but is really an outcome of the construction, so a first pass with assumed crimp should be checked against measured crimp on the sample and re-solved. Warp and weft contributions add back to the target exactly, which confirms the algebra but not the assumptions. Cover factor is reported unadjusted so it can be checked against the weave limit separately.
Using this calculator
About the Target GSM to Yarn Count & Construction Solver
The formula
This is the expression the tool evaluates. Every term is named underneath, with the unit it must be supplied in.
Crimped thread density, weft expressed in warp termsbracket = targetEpi x (1 + warpCrimp / 100) + targetPpi x (1 + weftCrimp / 100) / countRatio
Dividing the weft term by the count ratio restates the weft in units of the warp count, so the whole fabric can be solved for one unknown instead of two.
Warp count that lands on the target weightwarpNe = (590.5 / 1000) x 39.3701 x bracket / targetGsm
This is the GSM equation rearranged. 590.5 / 1000 x 39.3701 = 23.25, the same constant the forward GSM calculation uses — here it multiplies rather than divides because the unknown has moved.
Weft count and linear densityweftNe = warpNe x countRatio warpTex = 590.5 / warpNe
A count ratio of 1 gives the same count both ways; 1.5 gives a weft 50% finer in Ne terms, which is a lighter weft yarn.
The solved counts are only useful if the fabric can be woven. Peirce total cover approaches 28 at theoretical full cover, so a solution near or above that is a warning, not a specification.
Symbols used above
Symbol
Stands for
Unit
targetGsm
Target Fabric Weight
g/m²
targetEpi
Ends per Inch
EPI
targetPpi
Picks per Inch
PPI
warpCrimp
Warp Crimp
%
weftCrimp
Weft Crimp
%
countRatio
Weft to Warp Count Ratio
×
warpCount
Required Warp Count
Ne
weftCount
Required Weft Count
Ne
warpTex
Warp Count
tex
warpWeight
Warp Contribution
g/m²
weftWeight
Weft Contribution
g/m²
warpShare
Warp Share of Weight
%
coverFactor
Resulting Cover Factor
K
How the result is derived
Step by step, from the values you type to the figure on screen.
The forward GSM calculation is inverted: instead of asking what a construction weighs, it asks what count makes a construction weigh the target.
Both counts cannot be solved independently from one weight equation, so the count ratio ties them together and leaves a single unknown.
Crimp is applied to each thread system before solving, because crimped yarn carries extra length and therefore extra weight per square metre.
The warp and weft weight contributions are reported separately so the split can be checked against what the construction should look like.
Cover factor is calculated last as a sanity check on the solution.
What each input means
Where to read each value on the floor, the unit it must be in, and the range the tool accepts.
Input
Unit
Accepted range
Default
What it means
Target Fabric Weight
g/m²
20 to 1200 g/m²
150
Ends per Inch
EPI
10 to 400 EPI
120
Picks per Inch
PPI
5 to 400 PPI
60
Warp Crimp
%
0 to 40 %
8
Weft Crimp
%
0 to 40 %
6
Weft to Warp Count Ratio
×
0.3 to 3 ×
1
1 means both directions use the same count.
What the tool returns
The headline figure and every supporting value it is built from.
Output
Unit
What it tells you
Required Warp Count (headline result)
Ne
Count that delivers the target weight at this construction
Note the cover factor: 38 is well past the Peirce full-cover value of 28, so this sett and weight cannot be woven in a plain weave. Either the sett comes down or the target weight comes up — which is exactly what the solver is for.
How to use it
Work through the input groups in order — Target and Construction Assumptions. The defaults are a realistic case, so you can change one value at a time and watch what moves.
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.
Read Required Warp Count in the dark results panel — that is the headline figure, expressed in Ne.
Check the supporting rows underneath (Required Weft Count, Warp Count, Warp Contribution, Weft Contribution, Warp Share of Weight and Resulting Cover Factor) before acting on the headline — they are where an implausible input usually shows itself first.
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
Answering a buyer specification that fixes GSM and sett but leaves the counts open.
Substitution — a count is out of stock, so the ratio is changed and the tool says what the partner count has to become to hold the weight.
Feasibility screening before sampling, using the cover factor output to reject impossible combinations on the spot.
Cost engineering — sweeping the count ratio to find the warp and weft split that holds the weight at the lowest yarn cost.
Reading the result
Typical bands and what each one is telling you.
Value
What it indicates
Cover factor under 20
Open construction. Weavable comfortably; check opacity and air permeability are acceptable.
Cover factor 20 to 26
The normal working band for apparel woven fabric.
Cover factor 26 to 28
Dense. Weavable with good preparation, but expect beat-up force and stop rates to rise.
Cover factor above 28
Past theoretical full cover for plain weave. Revisit the sett or the target weight rather than the loom.
Assumptions and limits
The solved count will rarely be a commercial one — 29.9 Ne means ordering 30s and accepting the small GSM error, or adjusting pick density to compensate, and the second is usually cheaper. Crimp is an input here but is really an outcome of the construction, so a first pass with assumed crimp should be checked against measured crimp on the sample and re-solved. Warp and weft contributions add back to the target exactly, which confirms the algebra but not the assumptions. Cover factor is reported unadjusted so it can be checked against the weave limit separately.
Every input is bounded to the range normal practice occupies (Target Fabric Weight 20 to 1200 g/m², Ends per Inch 10 to 400 EPI and Picks per Inch 5 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.
Standards and further reading
Peirce, F. T. (1937), The geometry of cloth structure — the origin of the cover factor limit used as the feasibility check.
ASTM D3776 / ISO 3801 — the GSM the solution is being fitted to.
Questions people ask
Why solve for the count instead of the sett?
Because sett is usually the constraint that arrives with the specification — the buyer wants a particular EPI and PPI for hand and appearance — while the count is what the mill can actually shop for. When sett is the free variable instead, run the forward GSM calculator and sweep it.
What does the count ratio mean in practice?
It is weft count divided by warp count in Ne. A ratio of 1 means both yarns are the same count. Above 1 the weft is finer than the warp, below 1 it is coarser. Many shirting fabrics run a ratio near 1; bottomweight fabric often runs coarser weft.
The solved count is not one I can buy. What then?
Round to the nearest available count, then run the forward GSM calculator to see where the weight actually lands, and recover the difference with sett or crimp. Counts move in steps and GSM does not, so a solver result is a starting point for that adjustment rather than a purchase specification.
