Fabric GSM Calculator
Calculate GSM from sample weight, convert between GSM and oz/yd², and find total fabric weight. Free, instant, no signup.
How Fabric GSM is Calculated
GSM stands for grams per square metre. It is the universal measure of fabric weight per unit area, used by every knitting mill, weaving unit, and garment factory to specify, verify, and compare fabrics. Whether you are placing a fabric order, checking incoming rolls against the invoice, or calculating how much a finished garment will weigh, GSM is the number you start with.
The standard method uses a GSM cutter, a circular die that cuts exactly 100 sq cm of fabric (11.28 cm diameter). Weigh the cut sample in grams and multiply by 100. That gives you the GSM directly:
GSM = Sample weight (grams) x 100
If you do not have a GSM cutter, cut a rectangle of any known dimensions and use the general formula:
GSM = (Sample weight in grams / (Length cm x Width cm)) x 10,000
For accuracy, cut 3 to 5 samples from different positions on the roll (avoiding selvedge and the first few metres) and average the results. Industry-standard tolerance is plus or minus 5% of the stated GSM.
GSM Calculation for Knitted Fabric
Knitted fabrics (single jersey, interlock, rib, fleece) tend to have higher GSM variation across a roll due to tension differences during knitting and finishing. When measuring knitted fabric GSM, relax the fabric for at least 24 hours after removing it from the roll before cutting samples. Knit fabrics also stretch under their own weight, so measure on a flat surface without pulling. Common knitted fabric GSM ranges: single jersey 140 to 200, interlock 180 to 280, pique 170 to 230, fleece 240 to 380. The fabric GSM calculation formula is the same as above, but knit samples need more averaging (5 samples minimum) because of higher positional variation.
GSM Calculation for Woven Fabric
Woven fabrics (poplin, twill, canvas, denim, chambray) are more dimensionally stable than knits, so GSM readings are more consistent across a roll. The woven fabric GSM calculation formula is identical: GSM = (Weight in grams / Area in sq cm) x 10,000. Common woven fabric GSM ranges: voile and lawn 60 to 100, poplin 100 to 150, twill 150 to 250, denim 250 to 450, canvas 300 to 600. For woven fabrics, GSM is sometimes expressed as oz/yd² (ounces per square yard), especially in US and UK markets. Use the converter above: 1 oz/yd² = 33.906 GSM.
How to Use This Calculator
This calculator has three modes. Calculate GSM: select your sample type (standard 100 sq cm GSM cutter or a custom rectangle), enter the weight in grams, and get the GSM instantly. The calculator also shows the equivalent in oz/yd². oz/yd² to GSM: enter a value in either unit and convert to the other. Use this when comparing fabric specs from different suppliers. Fabric Weight: enter the GSM, fabric width, and length to calculate the total weight in kg. Use this to verify roll weights before accepting delivery or to estimate fabric order quantities.
International fabric sourcing often uses oz/yd² (ounces per square yard) instead of GSM. The conversion factor is 33.906: multiply oz/yd² by 33.906 to get GSM, or divide GSM by 33.906 to get oz/yd².
Frequently Asked Questions
How do you calculate GSM of fabric?
Cut a sample using a GSM cutter (100 sq cm area). Weigh it in grams and multiply by 100. For a custom-sized sample, use: GSM = (Weight in grams / (Length cm x Width cm)) x 10,000. Take multiple samples from different parts of the roll and average for accuracy.
How do you convert oz/yd² to GSM?
Multiply ounces per square yard by 33.906. For example, a 5.3 oz/yd² fabric is 5.3 x 33.906 = 179.7 GSM. To go from GSM to oz/yd², divide by 33.906. This conversion is commonly needed when sourcing fabric from US or UK suppliers who quote in imperial units.
What GSM is good for T-shirts?
Lightweight T-shirts (summer, promotional) use 120 to 150 GSM. Standard everyday T-shirts use 150 to 190 GSM, which is the most common range in Indian knit factories. Premium or winter T-shirts use 190 to 250 GSM. The right GSM depends on the yarn count, knit structure, and the buyer's specification.
How do you calculate total fabric weight from GSM?
Total weight (kg) = (GSM x Width in metres x Length in metres) / 1000. For example, 100 metres of 180 GSM fabric at 160 cm (1.6 m) width weighs (180 x 1.6 x 100) / 1000 = 28.8 kg. This is how you verify the weight of a fabric roll against the supplier invoice.
What is the difference between GSM and fabric weight?
GSM is the weight per unit area (grams per square metre), which is a fabric specification. Fabric weight (in kg) is the total weight of a particular piece of fabric, which depends on GSM, width, and length. Two rolls with the same GSM can have different total weights if their dimensions differ. GSM is the spec; weight is the quantity.