Over the weekend, I got a gauge question from someone planning to join the Anna Vest Knitalong, and since it’s a universal question, and a conundrum that I see people struggling with a lot, I thought I’d write it up for the blog. The question is: If you’re knitting at a gauge that’s different than pattern gauge, how do you figure out how big the garment will turn out?
Long-time readers know I rarely, if ever, knit a sweater at pattern gauge. We have it drilled into us as knitters that you have to match pattern gauge or your finished object will not match the pattern dimensions, which is absolutely true. If your stitches are bigger, your garment will be bigger; if your stitches are smaller, your garment will be smaller. So we swatch, and we measure. (See How to knit and measure a swatch.) And if our gauge is off, we dutifully swatch again on a different needle until we “get gauge.” Unless you’re like me, and you rarely use the recommended yarn, and you’re more interested in getting a fabric you like than in matching the pattern gauge, in which case you swatch to get your desired fabric and its measurements. However, going rogue means you’re going to have to do some grade-school math. (Watch for my upcoming post: Does getting gauge mean never doing math? Not if you care about fit.) (Actually, see How to start knitting a sweater for that.)
So Jennie swatched for the Anna Vest and she likes the fabric she’s getting on size 6 needles, which is giving her 22 stitches per 4 inches instead of the pattern gauge of 20 sts. She’s a 34″ bust and would have chosen to knit the size 34 vest (for a zero-ease fit), but given her smaller stitches, knitting the 34 would result in a garment that’s too small. The next size up is 38″ at pattern gauge, but what size will it turn out if she knits it at her gauge of 22 sts?
There are a couple of different ways to look at it:
1) Stitch count ratio: 20 divided by 22 is .909 — we can round that to .91 and say that Jennie’s stitches are about 91% the size of pattern gauge, so her sweater will be 91% of pattern dimensions. If she knits the 38, she’ll wind up with a sweater that’s about 34.5″ circumference. (38 x .91 = 34.58) Perfect!
2) Actual stitches per inch: 22 stitches per 4 inches is 5.5 stitches per inch. (22 divided by 4 = 5.5) The back piece of the Anna Vest in size 38 is 97 sts, 2 of which are selvage stitches (i.e., they’ll disappear into the seam at the end) so really it’s 95 stitches across. 95 sts divided by 5.5 sts per inch = 17.27 inches. Double that for the circumference of the garment = 34.5″. (That number being the cast-on count, it is the hem circumference. In this case, the body is straight-sided — no waist shaping, A-line shaping, etc. — so it is the same circumference at the hem and chest. If you’re working with a shaped garment, you’ll need to read into the pattern to find the stitch count at its largest point in the bust, usually right before armhole shaping begins, and use that number to calculate your adjusted chest circumference.)
To be thorough, don’t just look at the chest circumference. I’ve given a very detailed schematic in the Anna pattern, for instance, so take the time to calculate the changes in all of the widths and make sure there are no other areas of concern, such as shoulder width, neck width, etc. (Especially if you’re knitting a garment with sleeves — make sure they won’t wind up too tight or too loose.) If you decide to adjust stitch counts anywhere, bear in mind any necessary matching of stitch patterns at the side seams or stitch counts at shoulder seams, where it needs to match up with the back piece.
And there’s the matter of ROW GAUGE, the most critical factor in knitting that gets the least attention. Presumably Jennie’s row gauge is also tighter than pattern gauge. In the case of the Anna Vest, it’s not a significant concern. The lengths for the body and armhole are both given in inches rather than number of rows, so she’ll still just knit to those lengths — it will simply take her more rows to get there. All that will be affected is the few rows where the shoulder shaping occurs, which will be slightly shallower but not enough to make a meaningful difference in the outcome. Her neck shaping on the fronts will also be completed a little sooner than it would at pattern gauge, leaving her with a few more work-even rows at the top than she would have had otherwise, but that’s not a problem. For a pattern with more instruction given in rows than inches (or where a stitch chart is involved), there could be some concern about the armhole depth getting too shallow. If there were a sleeve cap involved, that might be cause for concern, as sleeve cap shaping happens over a greater number of rows, and you could wind up with a cap that’s a bit shorter than the armscye it’s meant to fit into. So just be on the lookout for anything where a difference in row gauge might be cause for adjustment.
And the number one thing to look out for if you’re knitting at a rogue gauge is if your row gauge is bigger than pattern gauge (fewer rows per inch). Shaping is nearly always distributed evenly over the length of an area, such as a body or sleeve, and nearly always given as “work the inc/decrease every Nth rows, X times.” If your row gauge is bigger — it takes fewer of them to make up that length — you’ll have fewer rows in which to complete those inc/decreases. So tally up the rows and shaping and make sure you can fit it all in, or recalculate the shaping according to your gauge. (See the Sweater math section of this post.)
It’s a big subject and I’m trying to not write a novel here, so I’m happy to answer further questions in the comments!