What is GSM ? Different GSM Calculation Formula of Woven and Knit Fabrics
Fabric buyers, sellers, or manufacturers involved in a fabric will all hear the term ‘GSM’.This term 'GSM' basically gives us some idea about the value of fabric, design, and quality, that is why it is very important to know about GSM. In this article, we will know, what is GSM? And I will discuss the calculation method of GSM of different types of fabric.
What is ‘GSM’
‘GSM’ means gram per square meter (gm/m2), it is a metric measurement unit of area or surface. GSM is expressed in gram generally. In some cases, it is expressed in the oz/sq.yard. Denim fabric weight is measured in ounces. Which is used for measuring weight per area of fabric or paper. It also gives an idea of the thickness of the fabric or paper. The higher the GSM of fabric, the higher the density of fabric and vice versa.
However GSM does not give a complete idea of thickness, thickness also depends on fabric design and structure.
GSM Calculation of woven fabrics
We can calculate GSM in different methods. In the case of woven fabric, we can calculate GSM from fabric structure. We can use the following formula for woven fabric
Fabric GSM = (EPI/warp count + PPI/Weft count) x (100+crimp %) X 0.2327
It is very important to know the crimp percentage of the fabric to calculate the GSM from the woven fabric structure.
Additionally, this is a longtime process and we may not get the right value in this method
The above formula will not apply to multiple crimp percentages in warp or weft, in which case we can apply the following formula.
Fabric GSM= ((EPI/warp count X 1.15) + (PPI/weft count x 1.1)) x 23.5
Where 1.15 warp crimp factor and 1.1 weft crimp factor
The above method is not very simple, because you need to know the number of warp and weft, crimp%. Moreover, its accuracy is questionable.
GSM Calculation of knit fabrics
Knit fabric is made using one yarn, showing a braided look to make continuous loop production. The knit fabric GSM calculation formula is given below.
Fabric GSM with indirect count (Ne) = Course per inch x Wales per inch x Stitch Length in mm x 0.9155 + Yarn count (Ne)
Fabric GSM with Direct count (Tex) = Course per inch x Wales per inch x Stitch Length in mm x 0.001549 + Yarn count (Tex)
GSM calculation of with GSM Cutter
‘GSM’ determine method is a physical test method known as an offline quality assurance system. we can easily determine the GSM of fabric by GSM Cutter without any data of the fabric.
How to calculate fabric GSM by GSM Cutter:
We can test GSM by GSM cutter in the following way
Apparatus required
GSM Cutter
Digital weight balance
Cutting pad
At first, cut the fabric from the sample fabric by GSM cutter
Weight the fabric by electric weight balance.
The GSM cutter is 100 sq. cm, so the weight of the cut sample will be multiplied by 100, this is fabric GSM,
If sample weight is 3.00 gm , then GSM = 3.00 (specimen weight) x 100 =300 GSM (gram per square metre)
In some cases, GSM needs to be converted to OZ / SQ.YDS, 1 Ounces per square yards (oz/sq.yds) = 33.9057 gram per square metre,
So, oz/sq.yds = GSM / 33.9057
Suppose, Fabric GSM = 300, then oz/sq.yds = 300/33.9057 =8.848 oz/sq.yds
However, to get the exact value of GSM is important to consider a few things. The moisture and atmospheric humidity may affect cotton fabrics and may require digital balance calibration. However normally +/- (3-5)% tolerance is acceptable from buyer requirement.
Engr. Md. Abdul Akher Sarker, BSc in Textile Engineering
Email: abakher.ctex@gmail.com Mobile: +880-1751499697
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