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.

All About Ajrak Process

This (http://www.ajrakhprinting.co.in) is an amazing website giving in amazing details the process of Ajrak Printing. Owned by Ranamal Khatri, the master craftman, this website can be used as an authentic one to study the process.I met Mr. Ranamal Khatri during my visit to Jodhpur. This site will give you a glimpse of the joy of watching Ajrak Made. This gives in details the process, the receipe, the comparison with the earlier process and a mouth-watering view of the products. To top it all, he has put in the process video wherein one can have a look at the process in action. And last but not the least, a look at the artisans working in his workshop and who have made it possible is given. Here are some pictures from the website:

Receipe

Video of the Process

Ajrak Saris

Artisans 

Awards won by Him 

There is a very good M.Des. Research done by B. Sinduja. You can access it here

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Vocabulary of Kantha

Here is a website that gives you the vocabulary of Kantha alongwith the basic stitches.

 

 

Types of Dyes used in Handblock Printing

The following is a brief description of the chemical dyes used in handblock printing in India:

Pigment dyes

Pigment colors are mixed with kerosene and a binder. The mixed color can be stored for a few days. The motif is printed directly on white or light-colored ground with a variety of pigment colors. Pigment colors are widely popular today because the process is simple, the mixed colors can be stored for a period of time, subtle nuances of colors are possible, and new shades evolve with the mixing of two or three colors. Also the colors are visible as one prints and do not change after processing. Colors can be tested before printing by merely applying it onto the fabric. The pigment color is made up of tiny particles, which do not dissolve entirely and hence are deposited on the cloth surface while rapid dyes and indigo sols penetrate the cloth.

Rapid fast Colors

In this process, the ground color and the color in the design are printed on white and/or light-colored grounds in one step. The dyes once mixed for printing have to be used the same day. Standard colors are black, red, orange, brown and mustard. Color variation is somewhat difficult and while printing it is not possible to gauge the quality or depth of color.

Discharge Dyes

These dyes are used if you need to print onto a dark background. Medium to dark grounds are dyed on fabric with specially prepared dyestuff . The printing colors then used on the fabric contain a chemical that interacts with the dye. This interaction simultaneously bleaches the color from the dyed ground and prints the desired color on its place. Areas can also be discharged and left white. The primary advantage of this process is that vivid and bright colors along with white can be printed on top of medium and dark grounds. 

    

Napthol

These are two sets of chemicals which upon reaction produce a third chemical essentially colorful in nature. Fabric is dyed in one and later printed with the other. The chemical reaction produces a third color. However, the biggest drawback of this process is that there are just a few chemicals available which produce colors upon reaction.

Source: http://www.aiacaonline.org/pdf/block-printing-extended-documentation.pdf 

See the images of these prints here : http://www.sashaworld.com/learn/learnframe.htm              

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