Yarn Substitution Guidelines
What do you do when you find a pattern that you love but the yarn is unavailable, discontinued or simply too expensive for your budget? Although it is generally best to use the original intended yarn to knit a pattern, it is quite easy to substitute something else if you need to. There are a few factors to take into consideration but there is no reason that your substituted yarn can’t create a garment just as fantastic as the original.
Gauge
Gauge is all important. All the measurements in the pattern, including numbers of stitches and rows, shaping and embellishments, are based on the gauge of the original yarn. If your substitute yarn has a different gauge you will be in for all sorts of problems and mathematical acrobatics.
Gauge is usually measured in a stockinette stitch swatch measuring at least 4 inches by 4 inches or 10 centimeters by 10 centimeters (nearly equivalent dimensions). For example, worsted weight gauge might be written as:
18 sts/24 rows over 4 inches/10 cm in st st
A pattern author may also supply gauge information in other stitch patterns. If the
pattern calls for circular knitting, then a swatch should also be knit in the round as gauge can vary between flat and circular knitting.
Nearly all yarns sold now have a gauge marked on the ball band, however row gauge is not always mentioned by the yarn manufacturer or pattern author. Since the length of knitted fabric is a direct consequence of row gauge, the pattern may have to be adjusted accordingly.
If the substitute gauge matches exactly, all is well. If it is very close, you can usually get gauge by varying your needle size slightly, test on a swatch first!
Yarn weight
Some effort has been made to standardize classes of yarns by weight. The weight categories can be used to identify good substitution options, although it is worth noting that some yarns may not fit easily in a single weight category. For example, Araucania Nature Wool is marketed as a worsted weight yarn, but could easily be classified as Double Knitting (DK) weight. For this reason, the weight categories should only be used as a suggestion and are no substitute for knitting swatches.
Wraps per inch (WPI) is an alternative method for determining yarn weight. Some designers may offer this as a guideline for finding good yarn substitutions.
Composition
The composition of the yarn (the fibres it is made from) is also important. A garment knitted in pure cotton will be completely different to one knitted in a ribbon yarn even if they have the same gauge. If you want your garment to have the same drape and appearance as the original then it is best to choose a yarn with the same or similar composition. However, you may be substituting yarn due to an allergy, or preference for a different fibre. If so, then look for something as similar to the original as possible.
Yardage
Finally, the big question is How much will I need?
Many patterns state the yardage per ball of the recommended yarn, and then it is a case of simple mathematics: multiply the number of balls needed by the yardage of the original yarn to find total yardage, divide this total by the number of yards per ball in your substitute yarn. If the yardage isn’t stated then you can generally find yarn information on the Internet. Do not run the risk of just buying the same number of balls that the pattern recommends for the original, yardage can vary greatly – and you just may end up with striped sleeves in a contrasting color when you run out!
These rules (and if all else fails, your Local Yarn Store assistant) should help you out in choosing an appropriate substitute yarn for your project. But no rule or shop assistant is infallible so before you launch in with your substitute yarn: knit a swatch!
Resources
Knitter’s Review article substitution guidelines