The Relationship between Needle Size and Yarn Weight

When making a gauge swatch, the relationship between the size of your needles and the weight of the yarn affects how the resulting fabric looks.

One thing that’s confusing for a lot of new knitters (and sometimes the experienced ones!) is that if your gauge has more stitches to the inch than you want, you need to go UP a needle size. You’d think “more means I need less, so a smaller needle!” but that’s not right. If you have too many stitches to the inch, then you need bigger stitches and that means a bigger needle. For example, if your gauge swatch has 26sts/4in and you need 24sts/4in, then you need bigger stitches – and therefore your next swatch should be knit with bigger needles. However, bigger needles will mean a looser fabric. That may or may not be what you want.

If your fabric is too loose, you can consider moving up a yarn weight. Looking back at determining yarn weight, you can pick a yarn of the same estimated weight but slightly lower wpi. Lower wpi = thicker yarn = denser fabric on the same needles.

Recap on making gauge swatch adjustments:

• Need fewer stitches to the inch: bigger stitches, bigger needles
• Need more stitches to the inch: smaller stitches, smaller needles

Side effects of changing needles or yarn weights:

• The same yarn on bigger needles = less dense fabric
• The same yarn on smaller needles = denser fabric
• Thinner yarn on the same needles = thinner, less dense fabric
• Thicker yarn on the same needles = thicker, denser fabric