Have you ever fallen in love with a pattern, only to find out the yarn it calls for is discontinued, sold out, or costs more than you want to spend on one project? Or maybe you’ve got a stash full of gorgeous yarn just waiting for the right pattern, but nothing in your stash matches what the pattern actually calls for.

That’s where yarn substitution comes in, and it’s one of those skills that sounds intimidating but really isn’t once you know what to look for. Get it right, and you can use pretty much any pattern with almost any yarn you love. Get it wrong, and you end up with a sweater that doesn’t fit, a blanket that droops, or a hat that could fit a watermelon (we’ve all been there).

So let’s break down exactly what to look at before you swap one yarn for another.

Why You Might Need to Substitute Yarn

There are a lot of good reasons to swap out the yarn a pattern calls for, and all of them are valid:

• The yarn is discontinued or you just can’t find it
• It’s out of your price range
• You want to use something you already have in your stash
• You have a wool sensitivity or prefer to avoid animal fibers
• You want the project to be machine washable
• You want to change the season a piece works for, like swapping a warm wool for a breezy cotton
• You just love a different yarn and want to use it

Whatever your reason, here’s what actually matters when you’re choosing a substitute.

1. Match the Yarn Weight First

Yarn weight is your starting point. Most yarns fall into a category like fingering, sport, DK, worsted, or bulky, and matching that category to what your pattern calls for is step one.

Here’s the catch though: not every yarn labeled “worsted” behaves exactly the same. Depending on how tightly it’s spun and what it’s made of, two yarns in the same weight category can still knit or crochet up a little differently. So weight is where you start, not where you stop.

A handy trick: wrap your yarn around a ruler for one inch, counting how many wraps fit snugly without overlapping or leaving gaps. Compare that count to your original yarn. If you’re within a wrap or two, you’re in good shape. Three or more wraps off, and you’re dealing with a real difference in thickness that will affect your project.

2. Check (and Swatch for) Gauge

This is the step people skip, and it’s the one that actually makes or breaks a substitution.

Your pattern lists a gauge, something like “18 stitches and 24 rows = 4 inches.” That number is what you’re actually trying to match, not just the yarn weight on the label. Cast on or chain enough for a swatch at least 4×4 inches (bigger is even better), work it up in your pattern’s stitch, and measure.

• If you have more stitches per inch than the pattern calls for, your stitches are too small. Go up a hook or needle size.
• If you have fewer, your stitches are too big. Go down a size.

One thing a lot of people don’t realize: you need to wash or block your swatch the same way you’ll treat the finished piece before you measure it. Blocking alone can shift your gauge by 5 to 15%, so a swatch fresh off the hook or needles can lie to you. Measure after blocking for the real answer.

It sounds like a lot of extra steps for “just a swatch,” but a 20 minute swatch can save you from ripping out 20 hours of work. Trust me on this one.

3. Think About Fiber, Not Just Weight

Even when the weight and gauge line up perfectly, fiber content changes how your finished piece looks, feels, and behaves.

Animal fibers (wool, alpaca, cashmere) have bounce and memory. They spring back into shape after being stretched, which is part of why they’re so popular for garments that need to hold their shape.

Plant fibers (cotton, linen) don’t have that same stretch. They tend to drape more and have a heavier hand, which makes them wonderful for looser, flowier pieces but not always the best swap for something that needs structure, like a fitted, ribbed sweater.

Acrylic sits in the middle. It’s consistent, machine washable, and honestly one of the most forgiving choices if you’re substituting for the first time.

A few swaps that tend to work well:

• Wool to superwash wool (same feel, easier care)
• Wool to a wool-acrylic blend (similar warmth, more budget friendly)

A few that need extra care and definitely a swatch:

• Wool to cotton (cotton is heavier and won’t bounce back the same way)
• Single-ply yarns to multi-strand yarns (different stitch definition, different pilling)

4. Recalculate Yardage, Not Just Skein Count

Here’s the step that trips up even experienced makers. If your pattern calls for 6 skeins of the original yarn, that does NOT mean you need 6 skeins of your substitute. Different yarns have different yardage per skein, so you have to do the math in yardage, not skein count.

Here’s how:

1. Find your total yardage needed: skeins called for x yards per skein
2. Divide that number by the yards per skein of your new yarn
3. Round up to the next whole skein
4. Add a little buffer, an extra 10 to 15%, or just one extra “safety” skein, to cover swatching and finishing

Quick example: Your pattern calls for 5 skeins of a yarn with 200 yards each, so you need 1,000 total yards. Your substitute yarn only has 170 yards per skein. That’s 1,000 divided by 170, which comes out to 5.9, so you’d round up and buy 6 skeins (maybe 7 to be safe).

A Bonus Trick: Holding Strands Together

If you’re trying to use up stash yarn that’s lighter than what your pattern calls for, you don’t always need to buy new yarn. Holding two strands together is a totally legitimate way to substitute for a heavier weight:

• Two strands of fingering weight ≈ DK weight
• Two strands of sport weight ≈ worsted weight
• Two strands of worsted weight ≈ bulky weight

It’s a great way to combine odds and ends from your stash into something new, just remember to swatch, since held-together yarns don’t always behave exactly like a single strand of that heavier weight.

Your Quick Substitution Checklist

Before you commit to a substitute yarn, run through this:

• [ ] Same weight category as the pattern calls for?
• [ ] Gauge matches after swatching and blocking?
• [ ] Fiber properties (drape, stretch, warmth) fit the project?
• [ ] Total yardage calculated, not just skein count?
• [ ] Care requirements work for you (machine washable if needed)?
• [ ] You like how the stitch pattern actually looks in the new yarn?
• [ ] You bought one extra skein, just in case?

Need Extra Help?

If you want a shortcut, yarnsub.com is one of my favorite tools for this. Plug in the specific yarn your pattern calls for, and it’ll suggest real substitutes based on weight, fiber, and yardage so you’re not doing all the math by hand.

At the end of the day, the best yarn for your project is the one that makes you excited to pick it up. A little math and a quick swatch is all it takes to make sure that yarn actually works, too.

Happy making!