Gauge describes the size of knitted stitches. It is a measure of how large the stitches are, and is defined by how many stitches and rows or rounds there are in one inch (or 4 inches) of knitted fabric.
::: EVERY KNITTER IS UNIQUE (when it comes to gauge):::
Every knitter is different – we hold our needles and yarn slightly differently, we are more tense or relaxed as we work. This means is that if I knit a square using aran weight yarn and 5mm needles, and Alexa knits a square using exactly the same yarn and needles, the two squares of fabric will likely be slightly different sizes because Alexa and I have different tensions.
The gauge stated on knitting patterns acts as a universal equalizer – it allows different knitters to follow the same pattern and achieve the desired size.
If a sweater pattern was simply written for worsted weight yarn and 5mm needles, then everyone’s sweaters would come out differently – there would be no way to predict finished size.
So instead of simply casting on with the needle size suggested in the pattern, when knitting garments you must make a ‘gauge swatch’, and determine the gauge that you achieve with the yarn and needles.
::: What is a swatch? :::
A swatch is a little piece of knitted fabric, usually about 6″ square-ish or round-ish. Making a gauge swatch gives you a bit of an insight into what your finished garment will look like. It shows you how dense will the fabric be, what gauge you achieve with a given needle size, and what the fabric will look like close up.
Rounds or rows? If you are working on an item that worked in rows, like a scarf or a cardigan, you will have a row gauge. If you are working on an item that is knit in the round, like a hat or a pullover, you will have a round gauge.
Why does this matter? Knitter’s gauges in rows and rounds can differ, even if we are talking about the same knitter on the same size needles. So, if you are going to be working in rows, your swatch should be in rows. If you are working in rounds, your swatch should be in rounds.
To make a flat gauge swatch, in rows, I typically cast on about 6″ worth of stitches using the needle size suggested by the pattern. If the pattern gauge is 5 sts / inch (5 sts x 6″ = 30) then cast on approximately 30 stitches. Knit a little square starting with a few rows of garter stitch, then working a section of stockinette stitch with little garter borders, then finishing with a bit more garter stitch (the garter edging makes the square lie flat, because stockinette stitch on its own curls).
To make a gauge swatch in the round it works almost the same way. You will want to cast on and join for working in the round (either casting on enough stitches to work on a 16″ circular needle, or on DPN’s for a smaller circumference, or using the magic loop technique. I like to work a little garter stitch to start, knitting 1 round then purling the next, then knit every round for a few inches, then work garter at the top.
After completing the square or tube, measure how many stitches and rows there are per inch. I use my handy gauge checking tool, but if you don’t have one you can just use a ruler. Take note of this number – it is your unblocked gauge. While you are working on the garment you can check to make sure your gauge matches this un-blocked gauge.
Next wash the swatch, dry it, and lay it out (this is called ‘blocking’… more on that here). Once dry, measure the stitches and rows per inch once more, and take note of the number again – this is the BLOCKED gauge. Many yarns change gauge quite drastically with blocking, and since you are going to block and wash your finished garment, the gauge after blocking is the really important one to know.
Now is the time to re-measure!
::: WHAT NOW? :::
If the gauge of your blocked swatch is exactly the same as the gauge required by the pattern, you are lucky! You can proceed to start the pattern using the needles you used to make your swatch.
If the gauge of your blocked swatch is different than the gauge required by the pattern, you need to make another swatch (I know I know, but it really must be done). If the pattern gauge is 5 sts / inch, and you got 5.5 stitches / inch, your stitches are TOO SMALL. You need to swatch again using a larger needle size. If the pattern gauge is 5 sts / inch and you got 4.5 sts / inch, your stitches are TOO BIG. You need to swatch again using a smaller needle size. Make sense?
Once you have finished your swatch you may want to label it. This can save you time later if you are using the same yarn and needles!
::: WHY BOTHER CHECKING GAUGE? :::
Say you want to knit a sweater to fit your 40″ chest. The pattern gauge is 20 sts / 4″ (or 5 sts per inch), and the suggested needles are 4.5mm (US 7). You choose a worsted weight yarn and cast on 200 stitches with the suggested needles. But you are a slightly looser knitter, and you get a gauge of 4.5 stitches / inch.
200 sts / 5 sts per inch = 40 inches (the sweater fits)
200 sts / 4.5 sts per inch = 44.5 inches (the sweater is 4.5″ too big at your chest… and probably WAY too big everywhere else. This is especially tragic because you spent 40 to 50 hours knitting it, plus spent significant money on beautiful yarn).
What seems like a very small difference in gauge has very significant ramifications in the finished size of a garment. Taking an hour to knit a gauge swatch can save you hours and prevent disappointing results.
::: SOMETIMES… gauge just doesn’t matter :::
There are, of course, projects in which gauge is not very important, because fit is less crucial. If you are working a cowl, or a scarf, a shawl, a blanket, or even a hat, slight differences in finished size will be less important or evident. For the blanket, cowl, and scarf, the finished size isn’t too critical. For the hat, there are really only so many stitches so you can only be off by so much. It’s also just a hat so a few hours of knitting to find out it’s too big or small isn’t as killer as a sweater (personal experience). So in these cases it is up to you whether making a gauge swatch is worthwhile!