A little bit of knitting math fun / geekery
Ok, so I’m working on a big new project. In the course of all of the planning, pattern-writing, and yarn-ordering, a question arose.
Why is it that some yarn companies list the stitch gauge on the ball band and omit the row gauge?
And while that question may really be unanswerable, it made me wonder whether there’s a formula that I could use to work out the row gauge (or at least a ballpark expectation of row gauge) from the stitch gauge.
One of the patterns that I’m working on will use a chunky yarn with a gauge of 3.5 sts / 5 rows / inch. I’m shopping for yarns online and would like to just make sure that the yarn that I order is perfect for what I want to do. Without having it here to swatch, I’d like to be able to do some quick calculations to double check.
When planning raglan sweaters from the top, the sweater grows in width at the same time as it grows in length. As I’m adding stitches to the chest I’m also adding rows to the armhole, and I need to keep track of both to make sure that when the sweater reaches my goal bust measurement the armholes aren’t too long or too short. So, for me, the row gauge is just as important as the stitch gauge.
This is where my science brain kicks in. I know that I’m wrapping a yarn of a given diameter around a needle of a given circumference. We can assume that the yarn is approximately the same diameter along its length, and that the same could be said for the needle. (We’re not talking funky fuzzy things or thick-and-thin things, just regular old yarns.) We also assume that we’re configuring the yarn in the same manner each time we perform a stitch. (We are working the gauge swatch in stockinette, not in a fancy stitch pattern.) All that being true, it *should* be true that the width of each stitch will always be some proportion of its height AND that that proportion is the same, regardless of diameter of yarn or circumference of needle. (Again, assuming that diameter of yarn and circumference of needle remain consistent over their lengths.)
I decided to look at a few common examples.
Mission Falls puts their stitch and row gauges right in the name of their most popular yarn: 1824. They expect 18 stitches and 24 rows in 4 inches.
If you divide 24 by 18, you get 1.333.
Another common gauge is 20 sts in 28 rows (or 5 sts / 7 rows / inch) Dividing 7 by 5 gets you 1.4.
I did the same calculation for a LOT of stitch and row gauges, and it turns out that they are proportionate!
You get approximately 1.4 rows for every 1 stitch!
My friend Alexandra the Tech Editor sent me a tweet confirming it! We are both officially math geeks, though she is much more proficient than I (she tweeted me with the 1.4 even before I’d come to the end of my testing!)
SO, if you’re ever shopping for yarn or patterns and confounded by the lack of row gauge…multiply the stitch gauge by 1.4 and you’ve got it.
August 8th, 2010 at 10:09 pm
What a useful little tip!
August 8th, 2010 at 10:39 pm
Which also implies – for those of us who never get row guage – that we all might have our own ratio. Hmmm. And given that I can always get stitch gauge I could probably then work out how much extra yarn I need b/c of my compressed row guage.
Speaking of which – would be interested in you applying your math geekery to the conundrum of what affects row guage? It doesn’t appear to be related to needle size or tension while knitting – that only seems to affect stitch guage – and I haven’t found any answers on that. Would help to know what to change to get a match for patterns that don’t given measurements only “Knit X rows”.
August 8th, 2010 at 10:45 pm
Exactly, Sue!
You should do several swatches in plain stockinette and do the same thing: Divide your row gauge by your stitch gauge. You may come up with your own personal ratio.
Then, you could use that to refigure the # rows you need to work for a given sleeve length, or in each section for bust, waist, hip, etc in order to get the proper shaping on your sweaters.
August 8th, 2010 at 10:57 pm
Ooh, I get Capital Letters.
Sue, if you ever figure out why some of us (by which I mean me) have compressed row gauge, I’d love to know.
August 9th, 2010 at 6:59 am
Math is geeky and awesome and i love figuring it out too! I’m sure there’s also a way to figure out, based on each knitter’s personal ratio number, the amount of yardage one might ACTUALLY use vs. what the pattern called for. I’m sure this calculation would take a bit more time to figure out – but something to get the mind going, eh?
August 9th, 2010 at 12:27 pm
Thank you SO much for that! I would never have had the patience to figure it out. Just another of the many reasons I love your blog!
August 9th, 2010 at 12:44 pm
Oooh–I think Sue has discovered a very useful part of your exploration–everyone should take the time to discover their own PERSONAL row gauge ratio. I find that while my students have little trouble getting stitch gauge for a given project everyone seems to complain that row gauge is hard to achieve. Knowing the difference between your own gauge and 1.4 would mean you’d know how to adjust patterns accordingly. How great!
August 9th, 2010 at 1:02 pm
This stuff gets me so excited. Knit geeks unite!
August 10th, 2010 at 6:19 am
That is so interesting – thanks for sharing! I was just figuring out my raglan “rate” last night for my upcoming vacation sweater (though it’s not quite a vacation with two little girls; while fun it’s more parenting in a different place without all your standard equipment). Guess I’d better go work out my personal ratio
August 10th, 2010 at 6:35 am
The 1.4 ratio makes perfect sense. The inverse is .7something or approx 3/4 which translates to the finishing instruction to pick up 3 stitches for every 4 rows.
August 10th, 2010 at 9:20 am
Awesome!!!
…. from one math geek to another
August 11th, 2010 at 8:44 am
I do not have a math brain and so I thank you for figuring out that ratio. Knitting can be very math intense, but luckily for me, also very forgiving.
August 11th, 2010 at 2:05 pm
Thank you! That is a very useful tip to know when heading out to the yarn shop!