Why Is the Fabric Weight Below the Standard? Troubleshooting from 8 Aspects

Insufficient fabric GSM (grams per square meter) may seem like a minor issue with little impact on regular trade. However, for export orders or specific trade transactions, GSM is often the most critical factor. It is not uncommon for enterprises to secure a large order only to face returns or claims due to substandard fabric GSM. Below are the reasons for insufficient fabric GSM.

1. Determining Fabric GSM

First, verify whether the yarn count and fabric density conform to specifications. Cut a rectangular or square sample from the fabric, ensuring its edges align with two warp yarns and two weft yarns. Measure the length and width (in centimeters) with a steel ruler to calculate the area of the cut sample (in square centimeters). Then weigh the sample on a balance scale (in milligrams).
Formula for GSM calculation of the sample:

GSM=1000Weight (mg)​÷10000Area (cm2)​=Area (cm2)Weight (mg)​×10

1.1 Combined Calculation and Tool Method

Example: A fabric sample measures 7 cm in length and 8 cm in width, with a weight of 772 mg.

GSM=7×8772​×10=138 g/m2

1.2 Tool-Only Method

Use a circular fabric sampler. Place the fabric underneath and rotate the cutter clockwise several times to cut three circular samples (taken at least 20 cm away from the selvedge or fabric end). Weigh the samples on an electronic balance to obtain the exact GSM value.

2. Calculating GSM of Dyed Fabrics

Grey fabric GSM refers to the weight per unit area of the fabric, usually expressed in grams per square meter (g/m²) or ounces per square yard (oz/yd²). The actual GSM is significantly affected by cotton blending ratio, yarn count, finished fabric width, and post-finishing processes. Below are simplified formulas for GSM calculation:

2.1 GSM Calculation for Non-Stretch Dyed Fabrics

GSM=(Warp Yarn CountGrey Fabric Warp Density​+Weft Yarn CountGrey Fabric Weft Density​)×24.3
Example: Calculate the GSM of a fabric with specifications 20×16 / 128×60 / 63″.

GSM=(20128​+1660​)×24.3≈246.6 g/m2

The actual GSM range is approximately 242–248 g/m².

2.2 GSM Calculation for Finished Stretch Fabrics

GSM=Finished Fabric WidthReed Width​×(Warp Yarn CountWarp Density on Loom​×22.17+Weft Yarn CountGrey Fabric Weft Density​×21.4)
Example: Calculate the GSM of a fabric with specifications C 78″ / 20×16+70D / 116×48.

GSM=5878​×(20116​×22.17+1648​×21.4)≈259 g/m2

The actual GSM range is approximately 260–265 g/m².

Note: 78″ refers to the reed width, and 58″ refers to the finished fabric width.

3. Comparison Between Simplified Calculation and Actual Weighing

Compare the GSM value calculated using the simplified formula with the actual weighed GSM of the finished fabric sample. Generally, a deviation within ±5 g/m² is considered acceptable. A significant deviation requires thorough analysis. Based on years of experience, the following patterns have been summarized:
A deviation within ±5 g/m² is normal under standard conditions. For significant deviations, follow these guidelines: Combed compact yarns tend to have smaller deviations.
  1. For polyester-cotton, polyester-nylon blended yarns, and chemical fiber yarns, the conversion constant is higher than the 583.1 constant used for pure cotton. Yarns of the same nominal count have a higher actual tex count, resulting in calculated GSM values being lower than the actual weighed values.
  2. Plied yarns are formed by twisting two or more single yarns together. Due to twist shrinkage, the actual yarn count is thicker than the nominal count, leading to calculated GSM values being lower than the actual weighed values. This deviation is more pronounced when both warp and weft yarns are plied.
  3. Open-end spun yarns are made of staple fibers and experience substantial loss during scouring in the pre-treatment stage of dyeing and printing, resulting in calculated GSM values being higher than the actual weighed values.
  4. GSM typically increases by 5–6.5% after washing treatment.
  5. For dark-dyed fabrics, the weight of the dye causes calculated GSM values to be slightly higher than the actual weighed values.
  6. For bleached or light-colored fabrics, calculated GSM values are slightly higher than the actual weighed values.
  7. GSM increases by 3–7% after coating treatment.
  8. GSM decreases by 3.5–6% after sueding treatment.

4. Reasons for Reduced Finished Fabric GSM

  1. Excessive stretching during pre-treatment leads to a reduction in weft density.
  2. Over-stretching the finished fabric to an excessively wide width.
  3. High alkali concentration and excessively high temperatures in post-processing damage the yarn fibers.
  4. Purchased raw yarn is thinner than the specified count (e.g., nominal 40S yarn actually measures 41S).
  5. Severe abrasion of raw yarn during weaving causes excessive fiber shedding, resulting in thinner yarn and lower GSM.
  6. Re-dyeing or stripping processes during dyeing lead to significant yarn loss and thinner yarn.
  7. Excessively high flame intensity during singeing dries out the fabric surface; subsequent desizing processes damage the yarn, making it thinner.
  8. Damage to the fabric surface during brushing or sueding finishing processes.
Post time: Aug-18-2025