When ordering fabric online, you’ll come across a few different measurement systems for fabric weight.
The most subjective and least informative is the system fabric.com uses. They list “lightweight,” “heavyweight,” etc., but they never define what those weight ranges are. I’ve ordered fabrics listed in the same weight category that vary a LOT from each other. I prefer to stay away from listings like this if I need fabric of a particular weight.
Better listings include some sort of actual measurement of fabric weight, but that’s only useful if you can use it to compare different fabrics. Here are the three most common systems you’ll see:
- Grams per square meter (gsm): this is the weight of one square meter of fabric, listed in grams. That means if you took a square piece of fabric that was one meter wide by one meter tall, and you weighed it in grams, you’d get this number.
- ounces per yard (oz/yard or oz/linear yard): this is the weight of one yard of fabric, listed in ounces. That means if you cut a yard of fabric and weighed it in ounces, you’d get this number. This is my least favorite measurement system because it depends on the width of the fabric. Obviously, if you had the exact same fabric, one yard that is 50″ wide would weigh less than one yard that is 60″ wide. It means you can only use this measurement to compare to other fabrics of the exact same width.
- oz per square yard (oz/sq yard): this is the weight of one square yard of fabric, listed in ounces. That means if you took a square piece of fabric that was one yard wide by one yard tall, and you weighed it in ounces, you’d get this number. This number is a lot more useful than oz/yard, but it’s also much less common to see.
So how do you compare different measurement systems for fabric weight? Well, converting between gsm and oz/sq yard is easy. You can use basic definitions that relate grams to ounces and yards to meters. Rather than reinventing the wheel, I’ll refer you to one of many online calculators that does this for you. Simple, right?
But what if you want to convert gsm to oz/yard or vice versa? Well, first you need to convert gsm to oz/sq yard, then use the width of the fabric to figure out the oz/yard. That’s a lot easier to do than it sounds! WOF = width of fabric, in inches.
oz/sq yard * WOF/36″ = oz/yard
oz/yard * 36″/WOF = oz/sq yard
That’s all. This works because the area of one yard of fabric is just the width of the fabric in yards * 1 yard. So, all you have to do is divide the width of the fabric by 36″ (the definition of a yard) to figure out the area of your one yard of fabric. Simple math for the win!
Even though this may seem really obvious, I was really confused by the oz/yard listings. I thought they were in oz/square yards, not oz/linear yards, for the longest time. When that lightbulb went off for me the fabric world made so much more sense.