A Guide to Yarn Substitution

Yarn substitution is where you use a different yarn from the yarn recommended by the designer who wrote the pattern you’re following.

There are all sorts of reasons you might want to use a yarn that’s different from what the designer recommends. Before you go subbing in your new yarn, though, think about the following issues. Understanding them will make your yarn substitution process more successful.

Compare Weight

The most important thing when choosing a yarn substitute is to pick a new yarn that is approximately the same thickness, or weight, as the recommended yarn. That’s because yarn weight is one of the key elements that affects the gauge of your knitting. If you substitute with a yarn that is drastically thicker or thinner than the recommended yarn, you won’t be able to achieve the right gauge. That, in turn, means you’ll have more trouble knitting a garment that will fit you right.

Different fibers behave in different ways. Designers choose yarns, in part, based on the fiber content. That’s because they know fiber content will affect the appearance of the garment. Generally speaking, plant-based materials will be heavier than animal fibers. Natural fibers will be easier to block than acrylics. When you’re choosing a substitute yarn, try to get one with a similar fiber content so your end result will have the same fabric characteristics.

Compare Fiber Content

This is a more subtle detail, but if you're making socks or colourwork, it can be significant. When a yarn is spun from a pile of fibers into a string, it’s turned a little bit as it’s stretched out to make a tubular shape. That turning gives the yarn some stability. Sometimes, those individual strings are then twisted together to form a stronger, denser yarn.

Compare Yarn Construction

Compare Your Gauge

Prepare to fiddle with needle sizes and maybe make a math adjustment or two if your chosen yarn doesn’t quite match the gauge in the pattern. If your gauge is too loose (that is, fewer stitches per inch than it should have), try going down a needle size. If it’s too tight (that is, more stitches per inch than it should have), try going up a needle size. Then repeat the swatching process.

Learn more about how to substitute yarn in knitting patterns on my blog. Plus, find helpful tips and tricks to improve your knitting, patterns, tutorials, and more.