The big question with gauge isn’t really how to get it, but “Will this sweater fit when I’m done?”
Let’s say your gauge is close but not quite. You’ve substituted yarn and changed needle sizes, and it’s pretty close to what the designer recommends, but maybe it’s coming out to in between sizes. How do you choose which size to knit?
The first thing to take into account is ease. A good pattern will usually tell you how much ease has been built in. What is ease?
Negative ease means the fit is tighter than the body measurements. It will be tight and stretchy.
Zero ease means the fit matches the body measurements. It will be form fitting but not stretched.
Positive ease means the fit is bigger than the body measurements. It will be trim but not form fitting with 2″ of positive ease. It will be a relaxed fit with 3-4″ of positive ease. More than that could be baggy, oversized, drapey, or breezy, depending on the garment style.
If the sweater you’re knitting is aiming for 2″ of positive ease, then you know you have some wiggle room with your stitches. As long you choose the size that knits up to be slightly bigger than your body measurements, it should work.
But first, here’s how to find out how large your sweater will be based on your gauge:
If your pattern’s called-for gauge is 4 Sts per inch, and your chest measurement is 34″, and the sweater measurement is 36″, then the pattern will likely tell you to cast on about 144 Sts (assuming the fit is straight and the stitch pattern is simple). Because 4 x 36 is 144.
But let’s say that you keep getting 4.5 Sts per inch. What size would your sweater be if you just knit it at that gauge? Well, 144 divided by 4.5 Sts per inch is 32″. Your sweater would end up being 4″ smaller in circumference. It would have 2″ of negative ease instead of 2″ of positive ease. Uh oh.
What if you’d like to stick with that 4.5 Sts per inch gauge and just cast on the right number? In that case, you’d multiply your Sts per inch (4.5) by the size you want (36″) to find the new St total around the chest, which would be 162 in this case.
But, you’d have to be ready to make other adjustments during the pattern, too. Changing the Sts can change the stitch pattern repeats (if you’re working cables, for instance), it can change the number of decreases or increases used, the cast on number, etc…. Better to just choose another size in the pattern and use the numbers the designer already calculated for you. (We use spreadsheets. And calculators. And percentages.)
So which size would you choose? Well, in this case, you’d choose a larger size for your stitches, but use the same length measurements as for the size you would have chosen so you don’t end up with too-long arms or a weirdly situated waist shaping.
Did this help you today, or is this whole sweater math thing still confusing? Leave me a comment and let me know. Tomorrow, I’m going to start showing you some little tricks for making nice edges in knitting.
This post is part of my 31 Days to Your Nicest Knitting series. Every day, I’ll post a new tip or trick to make your knitting nicer. You can follow along easily by subscribing. If you have any knitting problems you’d like me to fix, let me know and I’ll try to answer your question as part of the series. You can find all the posts in the series here.