How to Calculate Maximum EPI and PPI for a Fabric with Given Count

A Reader has asked me this question:

“ I want to know how to calculate max EPI and PPI of the given count. For Example, if we take 50s pv warp X 150 D  100% polyester weft, what will the max EPI and PPI if we weave it for plain, 2/2 twill,and satin.”

Here Mr. Ashenhurst can rescue us. The following method is based on his book “Textile Calculation and Structure of Fabrics”. Here the assumption is there is only one count of thread in both warp and weft. If there are two different counts of warp and wefts, threads per inch should be found out for both of them and then suitably adjusted.

The General formula to calculate Maximum EPI and PPI for a Given count of Warp and Weft

Now in a plain weave in a repeat there are 2 threads and 2 intersections. For 2/2 Twill in one repeat of 4 threads there will be 4 threads and 2 intersections.

Also as a rule please remember that 40s count yarn diameter is 1/165 of an inch.

To convert it to the yarn diameter of 50s warp we use the following formula

Which means for 50s PV Warp the diameter will be

Thus the Maximum Threads per inch for a plain weave will be 184 as this will be the diameter of the Yarn.

For 2/2 Twill be they will be ( From the Formula above)

Which means x will be equal to 122 threads per inch

Similarly for Satin weave one can find out the maximum ends and picks per inch

Please remember however that this is theoretical construct. Actual threads per inch are generally less than that.

To Calculate the Cotton Equivalent of 150 D, We use the formulaà count= 5315/denier, Which means it is equal to 35.43 or 35 count.

The Diameter for 35 count yarn will be ( Using the formula above) = 154.34 th of an inch

Then you can use the same equation to calculate the Maximum EPI and PPI

In these examples there is no allowance for bending, shrinkage or compression, the threads should be reduced or increased proportionately in case the fabric is subjected to bending, shrinkage or compression.

Indian Traditional Textiles- The document

traditionaltextiles.pdf

Sindhi Taropa Style of Kathiawar

The Sindhi Taropa denotes the interlacing stich embroidery-- the basic structure which is first built up with the use of long thread stitches into the surface and entire structure being built up thereafter by looping these threads, the overall effect produced is geometrical; floral patterns or figures, whatever is worked out through this type of stitch become-somewhat stylized. Practically the stitch is used as a means of achieving only an impression of the figure or motif which is aimed at.

How to calculate the weight of Fabric

How to Calculate the Weight of Fabric from Count, EPI, PPI and Width

One very common practical question in fabric sourcing is:

“If I know the yarn count, fabric width, ends per inch and picks per inch, can I estimate how much warp and weft yarn is required for 100 metres of fabric?”

The answer is yes. We can estimate it quite reasonably, especially for cotton woven fabrics, provided we understand the assumptions behind the calculation.

This calculation is useful for merchandisers, fabric buyers, converters, traders and small fabric suppliers because yarn prices change frequently. If the yarn price increases, the fabric price should also move logically. Without a basic calculation, it becomes difficult to judge whether the quoted fabric price is reasonable or inflated.

Suggested Visual 1: Fabric weight calculation map — count, EPI, PPI, width and crimp.

Information Required

To calculate the approximate fabric weight, we need the following details:

1. Warp yarn count
2. Weft yarn count
3. Ends per inch, also called EPI or reed
4. Picks per inch, also called PPI
5. Fabric width in inches
6. Warp crimp percentage
7. Weft crimp percentage

For a quick practical estimate, we may assume:

Parameter	Assumed Value
Warp crimp	10%
Weft crimp	3%
1 metre	1.0936 yards
1 pound	453.59 grams
Cotton count basis	840 yards per hank

Practical Note: Warp crimp and weft crimp are not fixed values. They change with weave, yarn type, fabric density, finishing and shrinkage. The values of 10% and 3% are only working assumptions.

The Basic Cotton Count Formula

In the English cotton count system:

\( \text{Cotton Count} = \frac{\text{Length in yards}}{840 \times \text{Weight in pounds}} \)

Therefore:

\( \text{Weight in pounds} = \frac{\text{Length in yards}}{\text{Count} \times 840} \)

This is the foundation of the fabric weight calculation.

Warp Weight per Metre

The warp weight per running metre can be calculated as:

\( \text{Warp weight per metre in grams} = \frac{\text{EPI} \times \text{Width in inches} \times \text{Warp crimp factor}} {\text{Warp count} \times 840} \times 1.0936 \times 453.59 \)

Where:

\( \text{Warp crimp factor} = 1 + \frac{\text{Warp crimp percentage}}{100} \)

For 10% warp crimp:

\( \text{Warp crimp factor} = 1.10 \)

Weft Weight per Metre

The weft weight per running metre can be calculated as:

\( \text{Weft weight per metre in grams} = \frac{\text{PPI} \times \text{Width in inches} \times \text{Weft crimp factor}} {\text{Weft count} \times 840} \times 1.0936 \times 453.59 \)

For 3% weft crimp:

\( \text{Weft crimp factor} = 1.03 \)

Suggested Visual 2: Warp and weft yarn consumption with crimp allowance.

Total Fabric Weight per Running Metre

The total fabric weight per running metre is:

\( \text{Fabric weight per metre} = \text{Warp weight per metre} + \text{Weft weight per metre} \)

This gives the approximate weight of one running metre of fabric.

To calculate the yarn required for 100 metres:

\( \text{Weight for 100 metres} = \text{Fabric weight per metre} \times 100 \)

Worked Example

Let us take a cotton fabric with the following construction:

Parameter	Value
Warp count	40s cotton
Weft count	40s cotton
Ends per inch	80
Picks per inch	72
Width	47 inches
Warp crimp	10%
Weft crimp	3%

Step 1: Warp Weight

\( \text{Warp weight} = \frac{80 \times 47 \times 1.10}{40 \times 840} \times 1.0936 \times 453.59 \)

\( \text{Warp weight} = 61.06 \text{ grams per metre} \)

Step 2: Weft Weight

\( \text{Weft weight} = \frac{72 \times 47 \times 1.03}{40 \times 840} \times 1.0936 \times 453.59 \)

\( \text{Weft weight} = 51.46 \text{ grams per metre} \)

Step 3: Total Fabric Weight

\( 61.06 + 51.46 = 112.52 \text{ grams per running metre} \)

So, the approximate fabric weight is:

\( \boxed{112.52 \text{ grams per metre}} \)

For 100 metres:

\( 112.52 \times 100 = 11252 \text{ grams} \)

\( 11252 \text{ grams} = 11.25 \text{ kg} \)

Therefore, approximately:

\( \boxed{11.25 \text{ kg of yarn is required for 100 metres of fabric}} \)

How to Calculate GSM from This

Many people confuse grams per metre with GSM.

Grams per metre tells us the weight of one running metre of fabric.

GSM means grams per square metre.

\( \text{GSM} = \frac{\text{Weight per running metre in grams}} {\text{Width in metres}} \)

For 47 inches width:

\( 47 \text{ inches} = 1.1938 \text{ metres} \)

Therefore:

\( \text{GSM} = \frac{112.52}{1.1938} \)

\( \text{GSM} = 94.25 \)

So this fabric is approximately:

\( \boxed{94 \text{ GSM}} \)

Common Confusion: A 47-inch fabric and a 60-inch fabric may have different weight per running metre even if their GSM is similar. Running metre weight depends on width; GSM is normalized to one square metre.

Suggested Visual 3: Difference between grams per running metre and GSM.

Practical Formula in One Line

For quick calculation:

\( \text{Fabric weight per metre} = \left[ \frac{\text{EPI} \times \text{Width} \times 1.10} {\text{Warp count} \times 840} + \frac{\text{PPI} \times \text{Width} \times 1.03} {\text{Weft count} \times 840} \right] \times 1.0936 \times 453.59 \)

This gives fabric weight in grams per running metre.

For 100 metres:

\( \text{Weight for 100 metres} = \text{Fabric weight per metre} \times 100 \)

Important Practical Notes

1. This is an estimate, not the final invoice weight

The formula gives the theoretical yarn weight in the fabric. In real production, the final weight may change due to sizing, desizing, bleaching, dyeing, finishing, shrinkage and moisture regain.

2. Crimp must be adjusted for fabric type

A plain fabric, twill fabric, satin fabric, dobby fabric and heavy canvas will not have the same crimp. Warp crimp and weft crimp should ideally be measured from the actual sample.

3. Width matters

The formula uses fabric width in inches. If the width increases from 47 inches to 60 inches, the yarn requirement increases proportionately.

4. Count system matters

This formula is for cotton count or English count. It should not be directly used for denier, tex or metric count without conversion.

5. Add process wastage separately

If you are calculating yarn purchase requirement, add suitable wastage.

\( \text{Purchase requirement} = \text{Calculated yarn weight} \times (1 + \text{Wastage percentage}) \)

If 3% wastage is assumed:

\( 11.25 \times 1.03 = 11.59 \text{ kg} \)

So, for production planning, you may require approximately 11.6 kg instead of only 11.25 kg.

Corrected Understanding of the Original Formula

The earlier formula was fundamentally sound:

\( \left[ \frac{\text{EPI} \times \text{Width} \times 1.10}{\text{Warp count} \times 840} + \frac{\text{PPI} \times \text{Width} \times 1.03}{\text{Weft count} \times 840} \right] \times \frac{1.09 \times 1000}{2.2} \)

But it can be made more accurate as:

\( \left[ \frac{\text{EPI} \times \text{Width} \times 1.10}{\text{Warp count} \times 840} + \frac{\text{PPI} \times \text{Width} \times 1.03}{\text{Weft count} \times 840} \right] \times 1.0936 \times 453.59 \)

The difference is small, but the corrected version is technically cleaner because it uses more accurate conversion constants.

Final Rule of Thumb

To estimate woven cotton fabric weight:

Fabric weight depends mainly on four things: yarn count, EPI, PPI and width.

Finer yarn means lower weight.
Higher EPI or PPI means higher weight.
Greater width means higher running-metre weight.
Higher crimp means more yarn consumption.

Once this logic is understood, fabric costing becomes much more transparent.

General Disclaimer

The calculations and explanations in this article are intended for educational and practical estimation purposes. Actual fabric weight may vary depending on yarn quality, weave structure, crimp, sizing, finishing, moisture content, shrinkage and testing conditions. For commercial costing, production planning or quality approval, calculations should be verified with actual sample testing and mill-specific data.