Substitute Yarn - Wraps Per Inch

If you are looking for a substitute yarn at the yarn shop (perhaps a less expensive or more durable yarn) for your project, bring a short double point needle and ruler to compare the wraps per inch between the suggested yarn and the one that you want to substitute. Just wrap the yarn around the double point with the coils touching, then measure how many fall within the inch. It will give you a good idea whether the two would knit to the same gauge. Here’s a handy chart for various yarn weights:

Yarn Weights

If you have the perfect pattern but not quite the right yarn to get started, use this general guide:
If you double lace weight yarn, you’ll get close to sport weight;
Doubling fingering weight gives DK weight;
Doubling sport weight gives worsted weight;
Doubling worsted weight gives super bulky weight.
Or you could use the problem as an excuse to go yarn shopping!

What Size Needle Do I Use For This Yarn?

If you are trying to figure out what gauge you would get by combining two or three yarns, here are a couple of tricks to help.
Math version: Add the stitches per inch together of the proposed yarns, and divide by 3.
Example 1: Combine 2 strands of fingering (sock). If each strand of fingering knits up at 7 st/in, the math is 7+7=14, 14/3=4.7, so the combined yarns are about worsted weight. If each strand of fingering knits up at 8 st/in, the math is 8 + 8 = 16, 16/3=5.3 so the yarns combine to a DK weight.
Example 2: Combine 1 strand of worsted and 1 strand of fingering. The worsted knits at 5 st/in and the fingering at 8 st/in. The math: 5 + 8 = 13; 13/3 = 4.3 st/in or a nice Aran equivalent.
Hands-on version: Take a knit gauge and thread the selected yarns through the hole which just fits the yarn. This gives you the needle size to use.