Needle size and gauge – The 4 most important things

Why does gauge matter?

To get a garment that's the right size, the most important thing is to knit at exactly the gauge stated in the pattern. Gauge means how many stitches and rows you need to make a 10 cm / 4" square.

Don't follow the needle size religiously — follow the gauge. Keep changing needle size until you reach the stated gauge.

The needle size given in a pattern is really just a starting suggestion — it's where I'd recommend beginning your search for the needle size that works for you. In practice, it also reflects the size I personally used to reach the stated gauge myself. My test knitters have sometimes reached the same gauge on quite different needle sizes. So don't get stuck on the idea that a pattern has to be knit on 3.5 mm / US 4 needles — the right size for you might turn out to be 4.5 mm / US 7, and that's completely normal.

To find your own gauge with the yarn you've chosen, you'll need to knit a swatch — sometimes more than one.

 

How do you make a reliable gauge swatch?

A gauge swatch is knit based on the stated gauge (for example, 20 stitches x 24 rows = 10 cm / 4").

Here's the essential part: never cast on exactly the stated number of stitches — make the swatch bigger. Always cast on 5-6 stitches more than the stated stitch gauge. So if the width gauge is given as 20 stitches = 10 cm / 4", cast on 25-26 stitches. Make the swatch wider so you can measure the gauge reliably, since edge stitches often curl inward.

The same applies to height. Knit more rows than the stated row gauge. If the row gauge is given as 24 rows = 10 cm / 4", knit at least 11 cm / 4¼". Make the swatch taller so you can measure the gauge reliably, since the cast-on and bind-off rows often curl.

Knit your swatch in the stitch pattern stated in the pattern. Swatches are often knit in stockinette, where it's easy to count stitches and rows from the right side using a measuring tape. For cables, knit a full cable panel, or 1.5 times the stated pattern repeat. A repeat and a half gives a more reliable stitch gauge measurement than just one repeat. For cables, rows are often easiest to count from the wrong side.

 

What do I do if I can't reach the stated gauge?

If you have more stitches per width than the pattern states, switch to thicker needles. If you don't change needles, fabric that's too tight will make your sweater too small.

If you have fewer stitches than the target number, switch to thinner needles. If you don't change needles, you'll get a sweater that's too big at the stated gauge with fewer stitches.

A swatch is your guarantee that you're about to knit something that will actually fit you.

Gauge also matters in the vertical direction — for example in sweater yokes — because patterns are often given as a number of rows to knit, not centimetres/inches. A yoke can end up too tall or too short if you don't stay on the stated gauge. So try to match the stated gauge in height too.

 

Am I allowed to unravel my finished swatch?

No! From this point on, the swatch is your most important tool — it's what lets you find out how to finish your knit, meaning how the yarn behaves when, for example, it's wet-blocked. Some yarns stretch, some develop a scent. Not every yarn even needs blocking. How you should treat a finished knit afterwards depends entirely on your project, since materials behave very differently.

That's why it's important to test different methods on your swatch, not on the finished garment, so you don't accidentally ruin the finished piece. If a yarn stretches unexpectedly, you'll end up with an oversized sweater. If you can anticipate the stretch using your swatch, you can use that knowledge and knit the sweater a bit shorter, then block it to the right length.

Yarn shops can help with the properties of different materials, since they knit with their own yarns constantly.