Our member (Steve Foreman, Teabreakknitter) has offered this guidance on knitting a tension square (gauge swatch). Although Steve retains copyright, you are free to copy this page for personal use.
Context
A gauge swatch is a key contribution to making a garment that fits. It helps you learn whether you should use the needles recommended in the pattern, or whether you need larger or smaller needles to get the gauge you need. It also lets you see and feel how the finished fabric will look, so that you can change the yarn. You might decide to knit a gauge different from that of the designer, so that the fabric is looser or denser, and choose to knit a bigger or smaller size in the pattern so that the finished garment is the size you want.
How to do it
A gauge swatch is a small piece of fabric that is knitted to allow the gauge to be calculated. Usually, the gauge is calculated by counting how many stitches there are in a 10 cm (4 inch) row of knitting, and how many rows there are in a 10 cm (4 inch) length of knitting.
A gauge swatch that is 10 cm wide and 10 cm high is not enough for measuring gauge. Stitches near the edges of the fabric tend to be a different size from the ones in the centre and will not be representative of the final garment. In addition, if the fabric has a texture pattern, such as lace or cables, the gauge will vary across that pattern, so the area over which the gauge is measured has to be big enough to average out those variations.
How big should my gauge swatch be?
You should aim for a gauge swatch that is at least 15 cm (6 inches) wide and high. It should also contain at least two repeats of and stitch pattern – which is likely to mean that your swatch is larger than 15 cm (6 inches).
How do you know how many stitches to cast on to make your gauge swatch?
- Look at the gauge needed by the pattern. If the pattern gives the gauge as the number of stitches and rows in 10 cm (4 inches), your starting point is twice that number of stitches or rows. If the pattern specifies the number of stitches and rows per inch, then you have to multiply the numbers by eight.
- Now look at the stitch patterns used. Is it plain stocking stitch or garter stitch throughout? Then you can make your gauge swatch using the numbers you got in the first step. If, however, the stitch types vary, then you may need to use twice the number of stitches (and rows) in the pattern repeat – if that is bigger than the number you need to make a 6 inch swatch.
Unless you are lucky, the actual size of your swatch will not be 10 cm (6 inches) – but that is part of the learning.
Knitting your gauge swatch
The influence of the cast-on and cast-off rows is larger for a gauge swatch than it is for the finished garment, so you want to make sure that your measurement of the gauge is not determined by them.
Start your gauge swatch by casting on the number of stitches you need using the basic stranded cast-on (this creates a series of loops that are held in place by the yarn tail).
Keeping to the stitch pattern you will be using in the project, knit as many rows as you need. Do not add a border in a different stitch pattern
Cast-off using the basic stranded cast-off (this just threads the trailing end of the working yarn through the loops of the final row of knitting).
Further consideration if your garment is to be knit in the round
Your gauge swatch should represent how the final garment will be knitted, but knitting a gauge swatch in the round is not straightforward, because it has to be laid flat to be measured. Most people knit at different tensions for knit and purl stitches, so knitting your gauge swatch as a flat item by working backwards and forwards would be misleading.
You can find a technique for knitting a gauge swatch to give a reliable gauge for items that are to be knit in the round in this video or on this web page. Alternatively, you could knit a hat and measure your gauge from that.
How to measure your gauge
Your aim is to find out how many stitches and rows there are in a 10 cm (4 inch) stretch of knitting. There are (at least) two approaches to this.
Count the stitches in a fixed distance
The most common advice is to lay a ruler or tape measure on the swatch horizontally (or vertically) and count how many stitches (or rows) there are in a 10 cm (4 inch) span. That is your gauge.
Measure the space taken by a set number of stitches
Personally, I find counting stitches along a row difficult and avoid doing it when I can. Because you will need to measure your gauge at least twice (and you may wish to measure it a third time), I recommend that you only count the stitches and rows once!
Lie your swatch on a flat surface and smooth it out by hand.
Start by taking a piece of coloured thread and sewing it along a row using running stitch – about 1 cm (0.5 inches) from the bottom of the swatch. Keep a long tail of thread on each side. Now do the same about 1 cm (0.5 inches) from the top of the swatch. The two threads will be running through the middle of the stitches. Now count the rows between the two threads, starting with the row above the bottom thread and ending with the row above the top thread. Add one (because there is half a stitch above the bottom thread, and half a stitch below the top thread). This gives you the number of rows to use in calculations (R).
Now you do the same, but this time run the threads vertically up between two columns of stitches, one about 1 cm (0.5 inch) from the left edge and one about 1 cm (0.5 inch) from the right edge. Count the number of stitches between these threads (you could use the horizontal threads as a guide to make sure you count along a row) and add one. This gives you the number of stitches to use in calculations (S).
Now you can calculate your gauge. Measure the distance across the swatch between your vertical threads (D), and the distance up between your horizontal threads (V).
If you are working in centimetres, then over 10 cm your:
stitch gauge is 10 x S ÷ D
and your row gauge is 10 x R ÷ V.
If you are working in inches, then over 4 inches your:
stitch gauge is 4 x S ÷ D
and your row gauge is 4 x R ÷ V.
If you have mixed inches and centimetres, try again using only one set of units!
When to measure your gauge
You should measure your gauge at least twice: when you have finished knitting your gauge swatch, and when you have washed and dried your swatch. You might also want to measure it again after a few days to see if it changes when the fabric relaxes.
Off-the-needle gauge
The “off-the-needle” gauge is not the gauge that is listed in a pattern, but it is a very useful tool for you to check your knitting as you go.
As soon as you have cast off you can measure your off-the-needle gauge. This is the gauge you can compare with the fabric as you knit your garment. I often find that my gauge loosens or tightens as I get used to knitting a fabric, and measuring the gauge while the knitting is still on the needles lets me see if this is happening. If I did not change, it would match the off-the-needle gauge.
Blocked gauge
Pattern designers use the “blocked gauge” in patterns. You need to measure this gauge if you want to make sure that you knit the right size garment.
Soak your swatch in luke warm water for at least 20 minutes – 2 hours is better. You may wish to mix a little wool soap into the water – if you do, rinse the swatch after soaking it.
After the swatch has soaked, squeeze it to remove most of the water, taking care not to stretch it. I then roll up the swatch in a towel and wring the towel to remove more of the water without stretching the swatch.
Next place the damp swatch on a blocking tile or other flat surface and smooth it out. Unless the swatch is lace (in which case you need to stretch it in the same way you would the final garment), let the fabric “find its own size” and pin it in place. Leave it to dry.
When the swatch has dried, you can unpin it, leave it a few minutes to relax, and then measure it to get the “blocked gauge.”
Fully relaxed gauge
If you are concerned that the yarn you are using might be very elastic, you might want to leave your swatch for few days or a week and re-measure the gauge. You might find that the gauge has changed because the wool has continued to move.
What to do if your gauge does not match that in the pattern
If your blocked gauge is not the same as that in the pattern, you have several options open to you. For many patterns the stitch gauge is more important than the row gauge – if your stitch gauge is wrong, then the width of the sweater or garment will be too small or too big. Many patterns tell you to “knit until the piece measures” a certain length, rather than specifying the number of rows, so the row gauge for these only becomes significant during shaping (such as some styles of arm hole). It is common for knitters only to match the stitch gauge.
If you have more stitches in a 10 cm (4 inch) row than the pattern, you could knit another swatch using larger needles. If you have fewer stitches, you could use smaller needles.
Another option is to calculate the finished size of the garment if you were to use your gauge. You might find, for example, that if you are knitting more loosely than the gauge in the pattern, knitting using the instructions for a size smaller than you were planning might give you a garment that fits. How can you find out what your finished size would be?
[Your finished size] = [Pattern finished size] x [Pattern gauge] ÷ [Your gauge].
So, if you have more stitches per 10 cm (4 inches) than the pattern, your finished item would be smaller than in the pattern. If you have fewer stitches, then it will be larger.
Other things to learn from your gauge swatch
Your gauge swatch can do more than tell you which needles to use and which size in the pattern to follow. You will have a sample of the fabric that you can feel to see whether your like the texture and drape. You can also see whether the stitch pattern looks as good in practice as it did in the pattern photographs. And in preparing your swatch, you will have practised the stitch patterns so that you will be more confident with them when you knit the item.
