How to Substitute Yarn Without Ruining Your Gauge
Weight, yardage, fiber, twist — the four numbers that decide whether a swap actually works, and the order to check them in.
Techniques · Purl Wise Editorial · Jul 2026 · 8 min read
Every knitter eventually stands in front of a pattern that calls for a yarn they can't get — discontinued, out of budget, or simply on the other side of an ocean. The good news: substitution is a skill, not a gamble. You just have to compare the right numbers in the right order.
Start with weight, but don't stop at the name on the band. "DK" from one mill can knit up closer to another mill's sport. The more reliable number is the recommended gauge: if the pattern's yarn suggests 22 stitches over 4 inches and your candidate suggests 22, you're in business — whatever the label says.
Second, check yardage per gram, not per skein. Two worsted yarns can both come in 100g skeins and differ by 40 yards, because one is denser. Divide yards by grams for each yarn: if the numbers are within about ten percent of each other, the fabric will behave similarly. If they're far apart, the denser yarn will make a heavier garment that grows when blocked.
Third comes fiber, and this is where drape lives. Wool has memory — it springs back, holds ribbing, forgives uneven tension. Cotton and silk have none: they stretch down and stay there. Alpaca is warm but heavy; superwash wool behaves more like cotton than you'd expect, because the process strips the scales that give wool its grip. You can absolutely swap fibers, but reread the pattern with the new fabric in mind: a ribbed hem in cotton will not snap back the way the designer's wool sample did.
Finally, twist and construction. A tightly plied yarn shows cables and texture crisply; a soft single blurs them into a halo. If the pattern is all about stitch definition, favor plied candidates. If it's a plain stockinette shape, a lofty single might actually improve it.
And then — swatch anyway. Not because the numbers lied, but because your hands are part of the equation. Wash and dry the swatch the way you'll treat the finished piece. Ten minutes of knitting beats ten hours of reknitting, every time.
Substitution is a skill, not a gamble — you just have to compare the right numbers in the right order.
When you browse patterns here, the yarn card on every pattern page ranks substitutes from the Ravelry database by weight, fiber, and community rating — and if you've told us what's in your stash, your own yarn gets ranked first. Numbers, checked in the right order, automatically.