The weight of a fabric depends of the thickness of the threads it’s made of, of the density of the weave or knit, as well as its composition (linen for instance is 20% heavier than silk). The dyeing or printing process can also affect the weight. Generally speaking, the lighter a fabric, the more drapey it will be, and the heavier, the more opaque and resistant it will be… but that’s not always true! A cotton poplin for instance will be lightweight (≈ 170 g/m²) but stiff, while a thick wool crepe will be heavy (≈ 300 g/m²) but supple.
Therefore it is particularly important when choosing fabric for a project to consider all its characteristics: its weight, but also its drape, stretch, breathability, softness, etc. With time and experience you’ll learn about different types of fabric and you’ll be able to follow your intuition when picking one, whether online or in stores. In the meantime, here is a little guide to help you decrypt this mysterious property that is fabric weight!
Cuts of fabric can have different dimensions, which is why fabric weight is measured in terms of mass per surface area, i.e. how much a given quantity of that fabric will weigh. Depending of the system (metric or imperial), the weight will be measured in grams per square meter (g/m² or gsm) or in ounce per square yard (oz/y², often abbreviated to oz.).
To convert from metric to imperial, you just have to divide the weight in g/m² by a factor of 33.906. For this wool Melton at 340 g/m² for instance:
340 / 33.906 = 10 oz.
Inversely, you can get the weight in g/m² from the weight in oz. by multiplicating by 33.906. For instance, for this 6.5 oz. denim:
6.5 * 33.906 = 220 g/m²
On some websites, you can find the weight given not in g/m² but in g/m or glm, which is grams per linear meter. Attention: this is not equivalent to the weight in g/m²! This is the weight of a cut of one meter of this fabric, so you have to take its width into account.
To find the weight in g/m² from the weight in glm, you simply have to divide the latter by the width of the fabric in meters, for instance for this wool coating with a width of 140 cm and a weight of 476 glm:
476 / 1.40 = 340 g/m²
The distinction between lightweight and very lightweight, or medium or heavy is very subjective. That said, many fabric websites have a relatively standard scale that categorizes fabrics in different weight classes. Here are the ones you’ll find most often:
Remember that the weight of a fabric is only one characteristic among others, and that sewing is not an exact science. If your pattern recommends a medium-weight fabric, and the one that you have your eye on seems “light-medium” rather than “medium-medium”, don’t fret! These indications are there to give you an order of magnitude, but a difference of 10 or 20 g/m² won’t have any impact on your final result.
To make buying fabrics online easier, we recommend you make a swatch notebook: for each fabric, write down its composition and its weight when you buy it. This will give you a whole rainbow of references to compare with the description of a fabric online, so that you can get a better idea of how it’ll be like before you click on “add to cart”!
We get many questions on fabric weight. If you’re trying to comprehend this, you are not alone! The weight of the fabric is measured in ounces per yard or meter: approximately 2-4oz for lightweight, 4-8oz for middleweight and 8-14oz for heavy weight. This chart would be very helpful as well and includes information on changing your sewing needle for the various weights. To keep from feeling stuck, first and foremost, read your pattern. It’s just the best place to find the proper fabric options for each sewing project. Here are some additional thoughts, tips and observations that have helped me in my sewing journey and I am confident they will help you as well.
There is a purpose and a work around for any “obstacles” I’m about to share but oftentimes the level of difficulty can increase on both extreme ends of the spectrum. Mid weight is a great place to start for a beginner sewer. The weight should be shown on the end of the fabric bolt if buying in person or listed under “fabric description” if buying from a website.
Projects I would suggest for lightweight fabrics are blouses, camis, gathered dresses and possibly a skirt. There are very often two things to keep in mind with lightweight fabrics. First, they are often see-through especially light colors *if not lined with another fabric, so think about if you mind your undergarments showing through. Second, if they are form fitting they aren’t forgiving- think silk skirts that people often grab shaping and smoothing undergarments for. For house projects, lightweight fabrics make lovely curtains if you’d like light to shine through and just provide a little privacy. They are also great for really nice tablecloths and napkins in a fine linen.
Projects for heavier weight fabrics include pants or trousers, canvas or linen totes, jackets and aprons. Think thick sturdy pieces with structure and often more warmth. For home projects you could choose small upholstery projects like fabric poufs, heavier window treatments for blocking out light and thicker throw pillows, or heavier aprons to name a few. Consider the type of sewing machine you will be using. If the fabric is super thick like heavy denim, canvas, leather, or some wool, your machine may not be heavy duty enough to sew through them especially when you reach an intersection that is more than two simple layers. My two sewing machines both handle 10oz fabric as the absolute limit and 8oz is even more ideal. *In this photo of Anna by the fountain, her pants are an 8oz heavy canvas type fabric and her stretch tank is most likely light to mid weight.
Projects for middleweight fabrics are endless. Midweight is truly king in this scenario. For home projects, quilts, tea towels, aprons, baby items or stuffed toys. For garments, tanks, blouses, dresses, flowy pants, shorts, sweatshirts, on and on. I think if you went through your closet you’d find that the majority of what you own falls in the middle weight category. This is probably due to the temperature versatility and comfort as much as anything else. Somewhere along the way we humans found the sweet spot. We knew that animal pelts and heavy weave wouldn’t cut it for day to day wear. They had to start somewhere! I’ll name a few fabrics in the 4-8oz range. A large variety of linen and cottons, satin, taffeta, poplin, polyester, and jersey but so many more.
The trick is knowing what type of garment or project you plan to sew. A structured button up work blouse could not be achieved with a bamboo/cotton stretch French Terry (which is a lovely fabric by the way but not for a button up dress shirt). When learning the difference in fabric weight, go into a fabric store and feel the fabrics. Maybe even take notes and write down some observations of your own. Once you establish your preferences, you can expand to shopping online. There are so many more options online. No small store can carry it all! Happy Sewing.