# How to Substitute Yarn in a Knitting Pattern
You found the perfect pattern, but the yarn it calls for is discontinued, out of your budget, or just not your color. Good news: you can almost always swap in a different yarn and still get a beautiful, well-fitting finished object. The trick is knowing which properties actually matter and how to translate the pattern's yarn requirements into terms that work for your new skein.
Yarn substitution comes down to three checks, in order of importance: weight and gauge, fiber content, and yardage. Get those three right, and the rest of the pattern's instructions will behave the way the designer intended.
Why Yarn Substitution Works (and Where It Goes Wrong)
A knitting pattern isn't really written around a specific yarn — it's written around a gauge. The designer chose stitch and row counts that produce a certain fabric density at a certain measurement. As long as your substitute yarn can be knit to that same gauge, the finished piece will come out close to the size and drape the pattern promises.
Substitutions go wrong when knitters match the wrong thing — say, picking a yarn because the color is right without checking whether it's anywhere near the same weight, or buying "enough skeins" without checking whether those skeins actually hold enough yarn.
Step 1: Match the Yarn Weight and Gauge
Every yarn label lists a weight category (sometimes shown as a number 0–7, from lace to jumbo) and a suggested gauge — typically written as stitches per 4 inches on a recommended needle size. Your first job is to find a substitute in the same weight category as the pattern's original yarn, or at least one that can hit the same gauge.
A rough guide to standard weight categories and their typical gauges over 4 inches (10 cm) of stockinette:
- Lace / Fingering: roughly 27–40 stitches
- Sport / DK: roughly 21–26 stitches
- Worsted / Aran: roughly 16–20 stitches
- Bulky: roughly 12–15 stitches
- Super Bulky and up: 11 stitches or fewer
These ranges are a starting point, not a guarantee — two "worsted weight" yarns from different mills can knit up slightly differently depending on ply and fiber. That's why the pattern's stated gauge, not the yarn label's suggested gauge, is always the number you knit a swatch against.
Don't Skip the Swatch
It's tempting to trust the ball band and cast on, but the only reliable way to confirm a substitute yarn will work is to knit an actual gauge swatch, measure it, and — if the pattern involves washing or blocking — treat the swatch the way you'll treat the finished piece before you measure it. Fiber relaxes, blooms, or drapes differently once it's wet, and a swatch measured straight off the needles can be misleading. If your stitch count is off, adjust your needle size up or down half a size and swatch again rather than pushing ahead and hoping.
Step 2: Consider Fiber Content
Once you've narrowed down candidates by weight, look at what they're made of. Fiber content affects two things a knitter cares about: how the fabric behaves (drape, stretch, warmth) and how it's cared for.
- Animal fibers like wool and alpaca have natural elasticity, which is part of why ribbing and colorwork patterns often assume some "bounce" in the stitches.
- Plant fibers like cotton and linen have little stretch and tend to hang heavier, giving fabric more drape but also more potential for growing over time, especially in garments.
- Blends and synthetics land somewhere in between and vary widely by the specific blend ratio.
You don't need to match fiber content exactly, but swapping a springy wool for an inelastic cotton (or the reverse) can change how a garment fits and hangs even at identical gauge. If the pattern is a structured sweater with fitted ribbing, staying within a similar fiber family will save you surprises. If it's a drapey shawl or a textured washcloth, you may have more room to experiment.
Care requirements matter too — a substitute that isn't machine washable is a real change for a pattern intended as an easy-care baby blanket, even if the gauge matches perfectly.
Step 3: Calculate How Much Yarn to Buy
This is the step where most substitution mistakes happen, and it's also the easiest to get right once you know the rule:
Always convert to total yardage before you calculate skeins — never assume "3 skeins of yarn A" simply becomes "3 skeins of yarn B."
Skein sizes vary enormously between brands and even between colorways of the same yarn line. A pattern that calls for three 200-yard skeins needs 600 total yards, full stop — and your substitute yarn might come in 100-yard skeins, 250-yard skeins, or anything else. The only number that transfers cleanly between yarns is total length, not skein count.
The Formula
Total yardage needed ÷ Yardage per skein of your substitute = Number of skeins to buy
Always round up, since you can't purchase a partial skein.
Worked Example
Say your pattern calls for three skeins of the original yarn, each holding 210 yards:
- Find the total yardage the pattern needs:
3 skeins × 210 yards = 630 total yards
- Check the yardage of your substitute yarn's skein. Suppose your chosen substitute comes in skeins of 137 yards each.
- Divide total yardage by your new yarn's yardage per skein:
630 ÷ 137 = 4.6
- Round up to the next whole skein:
You need 5 skeins of the substitute yarn.
Notice that skein count alone would have led you badly astray here — three skeins of the original became five skeins of the substitute, purely because the put-ups are different sizes. If the pattern gives yardage requirements by size (many patterns list yardage per size directly, which is even more precise than back-calculating from skein count), use that total yardage figure directly in step 1 instead.
Buy a Little Extra
Once you have your calculated number, consider rounding up by one more skein beyond the strict math, especially for garments. This buffer covers gauge swatches, dye lot differences if you need to reorder later, and the reality that yardage estimates in patterns are just that — estimates, not guarantees, especially if your row gauge runs looser than the designer's or you add length to sleeves or a body.
Common Yarn Substitution Mistakes
A few pitfalls come up again and again:
- Trusting weight category names alone. "Worsted" from one brand isn't identical to "worsted" from another. Gauge is the real test, not the label.
- Comparing skein counts instead of yardage. As shown above, this is the fastest way to run short mid-project.
- Ignoring row gauge. Stitch gauge gets most of the attention, but row gauge matters for anything with shaping calculated by row number, like raglan sleeves or heel turns.
- Skipping the wash-and-block test on your swatch. A swatch that looks right dry can shift significantly once treated the way the finished piece will be.
- Forgetting care instructions matter to the recipient. A gorgeous hand-wash-only substitute isn't a fair swap for a gift meant to go through a washing machine.
Quick Checklist Before You Cast On
- Substitute yarn is the same (or a compatible) weight category as the original
- You've knit and measured a gauge swatch that matches the pattern's stated gauge
- Fiber content is a reasonable match for the pattern's drape and care needs
- You've calculated total yardage needed, not just skein count
- You've divided total yardage by your new yarn's yardage-per-skein and rounded up
- You've added a buffer skein for safety, especially on garments
Yarn substitution is one of those skills that feels intimidating the first time and becomes second nature after a project or two. Once you're comfortable checking gauge, fiber, and yardage in that order, you'll be able to walk into any yarn shop or scroll through any online stash sale and know exactly what will work for the pattern in your queue.