Have you ever found yourself in this situation? You have a swatch of fabric; perhaps it came from a reference garment, or the source is completely unknown, and now you are trying to find a similar fabric for your design project, but you can’t identify the GSM. Read on to learn how you can do this in just three simple steps.
An Introduction to Fabric Composition
The GSM of the fabric is important because it tells you a lot about the composition and weight of the material. GSM stands for grams per square meter, commonly used in apparel manufacturing to convey an essential fabric property.
Fabric weight is sometimes measured in ounces per square yard (oz/yd²). No matter what unit of measure you are working in, the weight of the fabric is a key factor to consider when sourcing fabric for a project.
Understanding the fundamentals of fabric composition, such as what fiber is used and whether the fabric is knit or woven, are also key elements to consider.
For example: if you like the way a cotton double jersey knit drapes, but you decide to source a cotton twill instead. Even though the two fabrics might have the same weight and be composed of the same fiber content, these are completely different fabrics with different properties.
Furthermore, they will require different patterns to be developed due to the differences in the stretch. So it’s crucial to have some basic knowledge of fabric composition before you begin your sourcing journey.
Working with a seasoned pattern maker or fashion design consultant can be a great way to ensure you are on the right track. But if you are fairly confident you know what you’re looking for, let’s get right into it!
Calculating the GSM can be done with the simple method of taking a small swatch and weighing it.
To calculate the GSM:
Tools Needed:
Scissors
Ruler
Chalk or fabric marker
Cardstock for template (optional)
Precision Scale
STEP 1: Cut Your Fabric Swatches
Since GSM stands for grams per square meter and weighing an entire square meter of fabric isn’t always the most convenient way. Instead, we will weigh a 10 x 10 cm square of fabric. I suggest making a template out of cardstock, so you have it for future use, but you can use a ruler and chalk directly on your material to measure it. Cut out several pieces, about 4 - 5, so you can take the average from the swatches and get a more accurate number.
STEP 2: Weigh the Fabric Swatches
Using a precision scale, weigh the swatches and record each one. The scale should be able to weigh to the .001 of a gram. Note this type of scale is the kind typically used by jewelers, not the type you will typically find in your kitchen. I recommend this one as it comes with calibration weights and tweezers to ensure the scale is measuring accurately every time. STEP 3: A Few Math Calculations (Simple Math, so Don’t Worry!)
Now that you have your fabric swatches weighed, it’s time to average them out. Add them all up and divide the total by the number of swatches you weighed in step 2. Once you have the average figured out, you can multiply the result by one hundred to get your answer.
Here is an example of this in action:
Cut 1 weighs 3.05 grams
Cut 2 weighs 3.00 grams
Cut 3 weighs 3.01 grams
Cut 4 weighs 2.99 grams
3.05 + 3.00 + 3.01 + 2.99 = 12.05 / 4 = 3.01 x 100 = 301.25 GSM or ~300 GSM
Psst - If you're wondering why we multiplied by one hundred to get the answer, it’s because it would take one hundred 10x10 cuts of fabric to make up one square meter.
What if I need to know the weight in Oz?
Need to convert this to oz? Here’s the formula for that!
GSM / 33.906 = oz/yd²
So using our example above, it looks like this:
300 / 33.906 = 8.85 oz/yd²
There you have it; that sums it up, pun intended! If you found this helpful, make sure you subscribe to the blog so you can get more helpful tips on how to launch and run your successful fashion business.
Looking for a bit of help from a pattern maker and technical designer? If you are interested in getting your fashion designs developed, Digitech Design helps small and mid-sized brands with their apparel design and development with the help of 3D prototyping.
Using 3D state-of-the-art technology to test styles virtually with less waste and less hassle. Digitech Design has helped dozens of brands with design and development solutions providing physical samples, tech packs, sourcing, and more.
If you want to bring your ideas to life, book your consultation to get started!
About the author:
Ellie Wilcox is the founder and CEO of Digitech Design which helps entrepreneurs with apparel design and development. Providing services in 3D renderings created in Clo3D based on cad patterns and sewn prototypes. Ellie started working in fashion and production in 2011 and has implemented 3D samples since 2016. Using 3D reduces the number of physical prototypes to get to market and lessens the fashion industry's carbon footprint.
📲 Follow on Instagram @DesigningwithEllie
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