When you look at a sweater pattern and are trying to select the size to make you have to consider many things. The first thing to consider is your personal taste. Chances are in your wardrobe you already have a sweater that fits they way you want it to. It is probably among your most worn items. If this is the first sweater you are making then this is a great way to get the size you want. Measure this sweater and compare it to the finished sizes in the pattern you have chosen. Take the measurements of the chest size, the waist, the length, the width of the arms, and the circumference of the neckline.
The next thing to consider is the gauge of the swatch you make. The swatch is a lot like a map key. Without a swatch you are unlikely to get the result you want in a finished garment. Therefore, the swatch should be a minimum of four inches by four inches (or 10 cm. by 10 cm.). The swatch should be knit in the main pattern stitch of the sweater. If there are a lot patterns in the sweater mixed in with stockinette the swatch should reflect all of the stitches. Finally, the swatch should be washed, dried, and blocked based on the yarn manufacturer’s instructions and then measured for gauge. If you don’t get the gauge suggested by the pattern maker then you should do this process over again using different size needles.
All of the swatch or gauge steps may seem like a lot, but in the long run it will save you time and effort. The washed swatch will tell you if you like the way the fabric feels, drapes, looks like and it will tell what your gauge will be after blocking which is a better measure of finished size. A 4” x 4” or even a bit larger is still much smaller than the finished garment parts. We have all met knitters who never knit a gauge swatch and they say it always works, but I’m here to admit that I have garments in my closet that originally were meant for my husband, who is a foot larger than me and wider, but that fit me; all for the lack of a gauge swatch.
Now, back to the sweater size you are going to knit. Take your knit, washed, dried and blocked swatch, calculate how many stitches per inch or centimeters you have gotten. Multiply the stitches per inch by the inches in the finished sweater you want to achieve. For example, let us say your finished swatch had a gauge of 20 stitches in 4 inches. The stitches per inch is 5 (20 divided by 4), furthermore your favorite sweater has a chest size of 38 inches. Multiply 5 stitches per inch by 19 (which is half of the sweater) and you will get 95 stitches. Refer to your pattern and see which size casts on 95 stitches. At this point, I’d like to point out that making a copy of the pattern you are going to use is a good idea, circle, highlight or otherwise mark directly onto this copy the size you are knitting so that if you set the project down you will not forget what size you are knitting. (Did I mention my sweater closet, the one with the sweater that was supposed to fit my husband, when I was knitting that sweater and realized that there was no way it was going to fit him, I set it aside for awhile-okay a year. When I picked it up and started the sleeves I cast on for a different size than the body of the sweater. The sleeves fit him, the body fit me, the sweater went back to the pile for another year. I then made the correct sleeves for the original sweater and started fresh body for the first set of sleeves. It really was not a pretty process).
Once you have the size swatch made, blocked and measured; the size selected, the pattern copied and marked; you are ready to begin working on your sweater.