What Is Knitting Gauge and How to Calculate It?

If you are fairly new to the world of knitting you may have already been slightly concerned by the concept of ‘gauge’ and the fact that everyone always tells you it's very important and you have to check it before starting. I know how you feel, when I first started knitting I was so slow, but so keen to get my hands on my finished pieces. I had no time for this “gauge swatch”, and as my bewildered friends have commented “so you knit a square, and then undo it again?” Yes, yes you do..

So let start with what the gauge actually is. The gauge refers to the number of stitches required to reach a certain length and width of fabric. The gauge is written as stitches and rows per 4”/10cm, the lower the number, the larger each individual stitch and the less stitches are required per cm. As you might expect the thicker the yarn the fewer stitches there will be per cm, however it’s not just the yarn itself but also the needle size and the tightness of your knitting style that affect the final gauge.

Ok so far so good, but why does it matter?

Let's take an extreme example, you’ve seen a pattern for a simple scarf you really want to knit, and you’ve got a ton of lovely chunky yarn in your stash. The pattern suggests a size 4mm needle, but your yarn says 6mm, you don't have a 4mm needle and you just really want that scarf like now! No big deal it’s just 2mm right? so you go ahead with your lovely chunky yarn and 6mm needles. A few rows in you start to think, wow this is a very wide scarf.. That’s ok it’ll be cosy.. Fast forward a few hours, days, weeks, you run out of yarn and your scarf well it's a bit short, you don't want to start again, you buy more yarn and eventually you end up with a rather large scarf-blanket. So by now you probably know where I’m going with this, but let’s do the maths anyway!

Typical 4mm gauge = 22 stitches per 10cm

Typical 6mm gauge = 14 stitches per 10cm

Your scarf pattern calls for 66 stitches per row:

On a 4mm needle

66 / 22 = 3

3 x 10cm = 30cm

On a 6mm needle

66 / 14 = 4.7

4.7 x 10cm = 47cm

Ouch that’s 17cm or 63% larger than the pattern design, and remember the same will be true for the length, and the larger the piece the more yarn you need. Ok so that was annoying for the scarf, but imagine if your sweater ends up 63% larger or smaller than you intended.

This is why gauge matters and why pattern designers stipulate that you must choose a needle size to match their gauge. Ok so you have been convinced that the gauge is important and you want to make sure you get it right, but how do you check? This is where the swatch comes in, the swatch is essentially a mini square of the design you will be knitting.

In most cases the designer will tell you the pattern that the swatch should be made in, often this is stockinette stitch for sweaters but can also be garter or a different lace pattern used in the design. However, very rarely if ever will the pattern tell you how to actually make this swatch, how many stitches do I cast on? How many rows? Knit Purl? What’s the deal? At this point there is an assumption that you already know all of this. So let me help you out with some universal tips for making your swatch:

How to understand the stitch pattern required: Your swatch will typically be knitting flat (rows going back and forth), whereas your pattern may be in the round, therefore the stitch pattern for the swatch will not always be the same as the pattern for the design itself. Ok so, you are familiar with knit and purl, but stockinette, garter? These are not stitches, rather they refer to the appearance of the fabric produced. When viewed on the right side stockinette is all knit stitches and garter is alternating rows of knit and purl stitches. When knitted flat stockinette is created by knitting on the right side and purling on the wrong side, whereas garter is created by knitting both sides.

Number of stitches to cast on: I typically cast on the number of stitches in the gauge, plus 4. So if the gauge is 22 stitches per 10cm I will cast on 26 stitches.

How to stop your swatch from curling: If you just knit your swatch in stockinette the whole thing will curl up making measuring your gauge a bit of a nightmare, this is where those extra 4 stitches come in. Irrelevant of the stitch pattern used in your swatch knit the first 2 and the last 2 stitches of every row, both the right and wrong side rows, this will create a garter stitch edging at the sides of your swatch. To prevent the top and bottom of the swatch curling up again irrelevant of the stitch pattern, knit the first 4 rows, both on the right and wrong sides, this will create a garter stitch edge at the bottom, and repeat this for the last 4 rows.

How many rows to knit: To make a nice neat swatch you should knit your swatch until it is approximately square, using as many rows as you need.

How and when to measure the gauge: You can start measuring your stitches per 10cm fairly early on in the swatch, it’s worth doing this once you have about 1”/2.5cm height of your pattern. If at this point you have less stitches than required your needle size is too large and you can undo and start again with a smaller needle. If you have many fewer stitches than required start again with a larger needle. If you are close to the required number or slightly higher then continue making your whole square. Now comes the most important thing, you must wash and dry your finished swatch before measuring the final gauge. After washing your stitches will typically get larger, particularly in length, resulting in less stitches required per 10cm.

What’s more important stitches or rows? What may happen when you measure your gauge is that you are not able to find a needle size that gives you both the correct number of stitches and rows. Typically in most projects like sweaters the number of stitches is more important than rows, this is because the length can be adjusted by simply adding or removing rows, whereas the width is ‘hard coded’ in the design. On that same note, when you are knitting the body and sleeves of a sweater remember that after washing you may have a large increase in length. It’s therefore also a good idea to measure the gauge of your swatch before and after washing in order to estimate how long the final piece will be.

Hopefully this has cleared up some of the mysteries of the gauge and how to tackle it in order to create the most well fitting pieces!

A few extra tips:

Don’t fasten off your swatch after casting off, instead insert a washable clip stitch marker in the loop of the last stitch, this way you can easily undo your swatch to reuse the yarn.

Try using a gauge square, these are special plastic or wooden square rulers and they make a cute gift for knitters too.

Take detailed notes of your gauge including needle size and yarn, if you ever want to make another project with the same yarn at the same gauge you can skip the whole swatching process (although beware that your knitting style may evolve over time getting tighter or looser).