How to Substitute Yarn in a Pattern

You can use a different yarn from the one named in a knitting or crochet pattern, but a successful substitution involves more than choosing the same colour or the same weight category. The safest approach is to compare the label information, consider how the fibres behave, calculate the required length and then confirm the fabric with a washed gauge swatch.

1. Find the pattern’s yarn requirements

Start with the materials section of the pattern. Record the yarn name, number of balls or skeins, length per skein, weight per skein, fibre content, stated yarn weight and pattern gauge. Use the amount for the size you intend to make. If the project uses several colours, treat each colour as a separate quantity.

The original total length is the most important number for calculating the new quantity:

Original skeins × length per original skein = required yarn length

2. Compare yarn weight categories

A matching category is a useful starting point, not proof that two yarns are interchangeable. Terms such as DK, worsted and aran are broad, and manufacturers may classify similar yarns differently. The Craft Yarn Council’s numbered system runs from 0 Lace to 7 Jumbo, but its own guidance warns that one yarn in a category is not automatically interchangeable with another.

If the categories differ by two or more levels, treat the substitution as high risk unless you are deliberately redesigning the fabric or recalculating the pattern.

3. Compare length per weight

Two 50 g balls can contain very different lengths. Divide the length by the weight for both yarns. Similar metres per gram or yards per ounce suggest a closer thickness and construction, although fibre and loft can still change the result.

• Within about 10%: very close starting point.
• Within about 20%: often worth swatching.
• More than 30% apart: expect a meaningful difference.

These ranges are practical screening signals, not industry guarantees.

4. Consider fibre and construction

Wool is usually elastic and resilient. Alpaca often has more drape and less recovery. Cotton and linen can feel heavier and less elastic. Acrylic varies widely but may behave differently under heat and washing. Also compare whether the yarn is smooth, brushed, chained, tightly plied, loosely spun or a single ply.

A different fibre can be a creative choice, but the final fabric may change in warmth, stretch, drape, stitch definition and care requirements.

5. Check the gauge

Compare the pattern gauge with the suggested gauge range on the substitute label. If the target is inside or close to the range, the substitute is more promising. The label gauge is still only a clue: your own hands, stitch pattern, needles or hook all affect the fabric.

For garments, hats, socks and fitted projects, a washed gauge swatch is essential. A small difference repeated across many stitches can change the finished size substantially.

6. Calculate how many substitute skeins to buy

Divide the required yarn length by the length in one substitute skein, then always round up. A safety margin of about 10% is a practical default for swatching and small differences in personal tension. Colourwork, cables, modifications and fitted garments may justify a larger margin.

7. Make the final decision with a swatch

Work a sample in the pattern stitch, make it larger than the area you intend to measure, wash it as you will wash the finished project and let it dry fully. Measure the centre without stretching. Assess not only stitch count but also whether you like the fabric.

If the gauge works but the fabric feels too stiff, loose, heavy or unstable, the yarn is not a good substitute for that project.

Common substitution mistakes

• Buying by ball count instead of total length.
• Assuming every yarn in the same category behaves alike.
• Ignoring fibre, elasticity or care instructions.
• Measuring an unwashed swatch.
• Rounding the number of skeins down.
• Using a different dye lot for the final extra ball.

For industry terminology, see the Craft Yarn Council Standard Yarn Weight System.