How to Substitute Yarn in a Crochet Pattern (Without Ending Up With the Wrong Size)

If a pattern calls for a yarn you do not have, you can almost always substitute it. The rule is short: match the weight, get as close as you reasonably can on fibre, then check your gauge before you commit to the whole project. Colour is the fun part, and the part that matters least.

Here is how to make that swap without ending up with a piece twice the size you expected, or running out of yarn three rounds from the end.

Step 1: Match the weight number, not the word

Yarn labels carry a standard weight number from 0 to 7. That number is the single most useful thing on the label when you are substituting, because the words around it change from country to country. What one brand calls aran, another calls worsted. What one calls light, another calls DK.

• 2, fine or sport: thin, good for delicate work and tiny amigurumi
• 3, light or DK: the sweet spot for small plush characters
• 4, medium, worsted or aran: the most common beginner weight, easy to see and hold
• 5, bulky: fast to work up, chunky stitch definition

Stay on the same number and you are already most of the way to a safe substitution. Jump two numbers and the pattern will not behave. If the number on your label is unfamiliar, our guide to reading a yarn label walks through every symbol on the band.

Step 2: Look at fibre before you look at colour

Two yarns can share a weight number and still behave completely differently in your hands. Fibre is why.

• Cotton is firm with very little stretch. Stitches sit crisp and defined, which is why it suits amigurumi, but it is less forgiving if your tension wobbles.
• Wool is stretchy and springy. It blocks beautifully for wearables, and it can felt in the wash, which matters for anything a child will handle.
• Acrylic is springy, affordable and machine washable, though cheaper ones can look fuzzy and hide your stitch definition.
• Blends split the difference. A cotton and nylon blend, for example, keeps cotton's crisp stitches while the nylon adds a little give and strength.

Our own Yon Yarn is 68% cotton and 32% nylon in 50 g balls, chosen for exactly that reason: defined stitches without the splitting that frustrates beginners. If you want the longer comparison, see the best yarn for amigurumi.

Step 3: Swatch, even if you would rather not

A swatch is just a small test piece worked in the substitute yarn with the hook you plan to use. Work a square of about 10 cm for flat projects, or a small circle of the first few rounds for amigurumi, then count how many stitches fit across.

Compare that to the gauge the pattern states. More stitches than the pattern means your fabric is tighter and the finished piece will come out small. Fewer stitches means looser, and the piece will come out big. Ten minutes here saves an afternoon of unravelling. There is more on this in gauge in amigurumi.

Step 4: Adjust the hook, not the pattern

When your swatch does not match, change your hook size rather than rewriting the stitch counts. Too many stitches across, go up a hook size. Too few, go down. One size is usually enough, and a second try will get you very close.

Resist the urge to add or remove stitches to compensate. In amigurumi especially, the stitch counts are what create the shape, so changing them changes the character. If you are not sure which size you are reaching for, our hook sizing guide covers the usual beginner range.

Amigurumi plays by a different rule

For a plush character, exact finished size does not matter. Density does. The fabric has to be tight enough that stuffing cannot show through the gaps, so most amigurumi patterns ask you to go one or two sizes below the hook the label recommends.

That means a substitution which makes your finished character 2 cm shorter is a non-issue. What is not a non-issue: switching yarns partway through a project. If the head is worked in one yarn and the body in another, the two pieces will not match in size or texture, and it shows the moment you sew them together. Pick your substitute before round one and stay with it.

Step 5: Buy by metres, not by grams

This is the mistake that leaves people stranded near the finish line. Fibres have different densities, so 50 g of cotton is noticeably shorter than 50 g of acrylic. If a pattern says three balls, it means three balls of the original yarn.

1. Find the metres or yards per ball on the original yarn, and multiply by the number of balls the pattern lists.
2. Find the metres per ball on your substitute.
3. Divide to get the number of balls you actually need, then add 10 to 15% for safety.

Buy it all at once, in the same dye lot. Two balls of the same colour from different lots can be visibly different in daylight.

When to skip the substitution

Substituting is usually fine. A few cases where it is not worth the risk:

• Fitted garments where gauge determines whether the finished piece fits a real body
• Novelty yarn projects where the fluff or sparkle of the yarn is the whole point of the design
• Toys for small children, where washability and fibre safety matter more than what is already in your stash
• Following along with a video lesson, where matching the yarn on screen makes it far easier to see whether your stitches look right

The skill underneath all of this

Every step above assumes you can read what the pattern is actually telling you: the gauge line, the stitch counts in brackets, the abbreviations. If any of that still feels like code, our free Pattern Trainer teaches pattern reading as its own skill, in your browser, with no account needed to start. Once notation stops slowing you down, substituting yarn becomes a quick calculation instead of a gamble.

And if you would rather skip the guesswork entirely for your first project, every Yon Crochet kit arrives with the right yarn, hook and stitch markers already matched to the pattern, plus a video lesson filmed in both right-hand and left-hand versions (the left-hand lessons are filmed separately with a left-handed crocheter, so nothing on screen reads backwards). You can browse them all on our lessons page, or check the FAQ if you have a question before you start.