How to Substitute Yarns
Using your knitting math to replace yarns not in the pattern
We look at the basics of knitting math and how to create stitch ratios so that you can substitute yarns not called for in a pattern in order to obtain the correct gauge.
Sometimes creating a garment with the yarn called for in the pattern isn’t a possibility, and that can create problems in terms of reaching the right number of stitches in a pattern. However, all that is needed is some simple math to correct the problem, and here is how to do it.
First, make a swatch according to the pattern's gauge. If the pattern says that 21 stitches by 28 rows will be 4"x4", but the swatch is too small (or too large) look on the label that came with your yarn, then knit a swatch according to what gauge is indicated. Then, a little bit of math is all you need to know to figure out your correct gauge and ratio.
For example, the pattern calls for 21 sts x 28 rows, but you need to knit 25 sts x 32 rows in order to achieve your 4"x4" swatch. You require more stitches to achieve a certain length, and therefore will have to increase the number of stitches to cast on in order to achieve the right sizing. This is where the math comes in.
A ratio is the answer - and in order to do that some division is that’s required. First do the stitches per row. The pattern calls for 21 stitches but 25 stitches to get 4" is needed. Take your number of stitches and divide by the called for number of stitches. It’ll look like this:
25 ÷ 21 = 1.19
It’ll actually return a long string of numbers, but all that is needed is the first decimal point, and it's generally a good idea to round up, so go with 1.2. For every 1 of the pattern's stitches 1.2 will have to be made. This might not sound like a big difference, but over 100 stitches it will be.
Now that the stitches are done, what about the rows? Do the exact same thing; divide your number of rows by the pattern's number of rows. It'll look like this:
32 ÷ 28 = 1.14
Once again round up to 1.2. It won't always work out that way - sometimes the stitch ratio will be 1.2 and the row ratio will be 1.1 or 1.3. Remember to do the math, and write it down.
Now apply your math to the rest of your pattern. If a pattern calls for you to cast on 112 stitches, you take that number and then multiply it by your ratio. It'll look like this:
112 x 1.2 = 134.4 stitches
There’s your number of cast on stitches. Notice that it's in decimal form, and since .4 of a stitch can’t be cast on, look at the pattern and decide if you will cast on 134 stitches or 135. If the pattern is calling for a repeat stitch pattern in an even number (like a rib), cast on 134 stitches. If the stitch pattern calls for an odd number of stitches, cast on 135.
Next, look at the sizing. Some patterns are written in inches rather than numbers of stitches - for example, “begin waist shaping three inches after casting on”. If that is the case, simply follow the pattern as is. However, if your pattern says begin waist shaping after 50 rows, use your ratio. It'll look like this:
50 x 1.2 = 60 rows
So begin your waist shaping at 60 rows instead of 50.
Once that basic math is down pat, it’ll be easier to substitute any yarn in a pattern, and create a perfectly fitted garment.
© Kelly Gilliam, text and images. Reproduction without permission is prohibited
