Found a pattern you love, but want to use a different yarn? You can sometimes substitute 8 ply for 10 ply, or the other way around, but it is not a straight ball-for-ball swap. The safest choice matches the pattern’s gauge, creates the right fabric and gives you enough metres to finish.
For a fitted garment, start with the weight the pattern specifies. For a blanket or scarf, there is often more room to experiment if you are happy to adjust the finished size or stitch count.
What is the difference between 8 ply and 10 ply?
In Australian yarn terminology, 8 ply commonly corresponds to DK, while 10 ply commonly corresponds to worsted or aran. These names are useful starting points, not precise measurements. Modern ply labels describe a weight category rather than reliably telling you how many strands were twisted together.
10 ply is generally thicker than 8 ply. It usually produces fewer stitches per 10 cm and a heavier fabric, but yarns within either category vary. Always compare the individual yarn’s details and your own swatch.
If your pattern calls for DK, start by browsing our 8 ply yarns. For a pattern calling for 10 ply, worsted or aran, explore our 10 ply yarns and check the recommended gauge against your pattern.
1. Let gauge decide, not the label
Gauge, also called tension, is the number of stitches and rows in a measured area, usually 10 cm. Your pattern’s gauge is the target; the ball band is only a guide.
For example, if a pattern needs 22 stitches per 10 cm but your swatch has 20, the same stitch count will make a wider piece. A section of 110 stitches would measure about 50 cm at the pattern gauge, but 55 cm at your gauge. That difference matters in a jumper.
Smaller needles generally give more stitches per 10 cm; larger needles generally give fewer. Adjusting needle size can help, but do not force a thicker yarn into a stiff fabric or a thinner yarn into a loose, see-through fabric just to reach the numbers. Match both gauge and the feel of the fabric.
For crochet, use the same principle with hook size and the pattern’s stitch pattern. Check row gauge too, especially for shaped pieces, sleeves, yokes and patterns worked to a fixed row count.
2. Compare metreage per 50 g
A 50 g ball is a weight, not a promise of a particular length. Two balls weighing the same can contain very different amounts of yarn.
To compare labels on equal terms, calculate: metres per 50 g = metres in the ball ÷ ball weight in grams × 50. A 100 g ball containing 200 m works out to 100 m per 50 g.
With similar fibre and construction, more metres per 50 g often suggests a finer yarn. However, a light, airy yarn can have more metres than a dense yarn of similar thickness. Use metreage alongside gauge and fibre, not as a substitute for swatching.
Estimate purchases by total metres rather than matching the original number of balls. For example, a pattern using eight 50 g balls at 100 m each calls for 800 m. A replacement with 90 m per ball would need at least nine balls to reach 810 m, before allowing for swatching, changes or a safety margin. This is a starting estimate only: changing yarn weight or fabric can change consumption. Round up to whole balls and, where possible, buy enough in the same dye lot.
3. Match fibre behaviour as well as thickness
A yarn can match stitch gauge and still behave differently in the finished project.
- Wool: often has spring and resilience, useful for ribbing and fitted garments. Washing behaviour varies, so check the care instructions.
- Cotton and linen: usually have less elastic recovery than wool and can feel heavier or grow under their own weight. Be cautious when replacing wool in a close-fitting garment.
- Alpaca: often creates a soft, draping fabric but may have less bounce than wool. Check for stretching after washing and hanging.
- Acrylic and blends: vary widely in drape, warmth and recovery. Check the blend and care label rather than assuming they behave alike.
Construction matters too. A fluffy, brushed yarn will not necessarily give the same stitch definition as a smooth, tightly spun yarn. For cables, ribbing or textured stitches, swatch in the actual pattern to see whether the detail still works.
4. Make a washed swatch before committing
- Use the proposed yarn and your starting needle or hook size. Work in the stitch pattern specified for the pattern’s gauge. If the project is worked in the round, swatch in the round or use a method that reproduces your in-the-round tension.
- Make the swatch larger than 10 × 10 cm, ideally around 15–20 cm across, so you can measure away from the edges.
- Wash and dry it as you intend to care for the finished item, following the yarn’s care instructions. Let it dry fully and settle before measuring.
- Count stitches and rows across the central 10 cm without stretching the fabric. Compare both measurements with the pattern.
- Check softness, drape, stitch definition and recovery. For a heavy project, consider how the fabric behaves under its own weight.
- If necessary, change needle or hook size and repeat. If reaching gauge spoils the fabric, choose another yarn or a pattern written for that weight.
Keep your swatch and notes until the project is finished. A few extra minutes here can save hours of unravelling.
When is substitution safer for a blanket?
Blankets, scarves and simple rectangular projects are usually more forgiving because a small change in size does not affect body fit. Using 10 ply in an 8 ply blanket pattern may produce a larger, heavier blanket with the same stitch count. Using 8 ply in a 10 ply pattern may produce a smaller, lighter one.
Swatch first, then estimate the starting stitch count from your washed gauge: desired width in centimetres × stitches per 10 cm ÷ 10. Adjust that number for the pattern’s stitch repeat and borders. Calculate length from your row gauge, or work to a measured length if the pattern allows it.
Check the whole design before changing counts. Motifs, corner-to-corner construction, borders and fixed repeat layouts may need more planning than a simple rectangle. Re-estimate yarn quantities rather than assuming the original metreage will cover a different size or weight.
When should you avoid a swap for a fitted garment?
For jumpers, cardigans and other fitted garments, the lowest-risk substitute is a yarn in the same weight category with similar fibre, construction and washed gauge. Check the pattern’s finished measurements and intended ease, not just the size name.
If 10 ply only reaches an 8 ply pattern’s gauge when the fabric feels rigid, do not force it. If 8 ply only reaches a 10 ply gauge when the fabric is too open or unstable, choose a different yarn. A garment pattern written for your chosen yarn weight is often the better option.
Avoid simply knitting another size to compensate for a gauge mismatch. Necklines, armholes, sleeves and shaping may not scale together. Even when stitch gauge matches, different row gauge can affect raglan depth, sleeve shaping and overall proportions.
A quick check before you shop
- Write down the pattern’s stitch and row gauge, stitch pattern and original total metreage.
- Compare yarn weight, metres per 50 g, fibre content, construction and care instructions.
- Choose a yarn that makes the right fabric after washing, not merely one with a similar label.
- Allow for a swatch and extra yarn, and check dye lots where relevant.
- For fitted garments, prioritise matching gauge and fabric. For blankets, decide whether you will accept a size change or adjust the stitch count.
Ready to choose? Shop our 8 ply yarn collection for DK-weight projects, or browse our 10 ply yarn collection for thicker projects. Compare each yarn’s specifications with your pattern, then let a washed swatch make the final decision.