I’m excited about your continued interest in this series! It’s fun to be able to share the design process with you.
From last time: I got several questions about why I can’t seam with the tweed. I find that the uneven nature of tweeds, with their bumps and snags and often-fragile construction, results in uneven seams and a lot of broken yarn when trying to sew things together. It always seems to take twice as much irritating effort to get seams that meet my standards–so when I have to seam tweed I always use a similarly-colored strand of smooth yarn for my mattress stitch. Your mileage my vary.
On to the new!
The very next thing I do is write my pattern, in all 10 sizes. I leave very little left undone at this point–by this time I have my pattern-writing routine down pretty well, and I typically only leave things like necklines and sleeve caps as “TBD” before picking up the needles for the first time. (And even those TBDs get ironed out before I actually knit them.) That way, my knitting of the sample serves as a test-knit for the pattern, too. I won’t bore you all with a description of the pattern writing process itself; suffice it to say that it involves spreadsheets and a lot of arithmetic.

What I really want to talk to you about today is how I choose which size to make (and how I’d love to encourage you to choose, too).
To fit you well, sweaters need to fit your shoulders/upper torso well. This is true for men’s suits, and it’s true for our sweaters. This is the single most involved area of a sweater to modify–so much more involved than dealing with the bustline or a pot belly or short arms or a long torso or what have you. If you are a not-particularly-broad-shouldered, B-cup or below woman, you can get away with choosing based on your full bust size just fine. Otherwise…
…otherwise things get a bit trickier. What you really want to do is choose a sweater size based on your upper torso measurement. What’s that, you ask? In short, that’s the way to ensure that your sweaters will fit your shoulders/upper torso. You take it by measuring yourself around your torso, way up in your armpit. This is above the bulk of your bust (and if the girls are especially perky, push ’em down a bit). If you are a large-busted woman, this number is likely much lower than your full bust measurement. If you have broad shoulders and a small chest, this number might well be larger. However it relates to your bust measurement, this is the one you need to go by.
My numbers are as such: Upper torso is 38”, full bust is 40”. I make size 38” sweaters.
Now, I like the look of an especially tailored, fitted sweater. Not everyone does! But whatever style you choose, choose it based on that upper torso measurement.
What do I mean? Well, for a sweater like Ayana, which is meant to be worn with just a smidgen of ease in the bust, I knit the 38” size and give myself a couple of vertical bust darts to ensure the ribbing doesn’t pull overly tight across the fullest part of my bust.
For a much more relaxed cardigan, where the designer has said something like “Intended to be worn with 2-4” of positive ease in the bust.”, I choose a size that gives me 2-4” of positive ease over my torso measurement, or whatever size has a finished bust measurement of between 40 – 42”.
Of course, this will often ensure that you need to make other modifications to the pattern. For women with large busts, this typically means you’ll need some short row shaping or vertical bust darts so that the front of your sweater doesn’t ride up past your bellybutton. (Since I have a booty to match my bust, I typically just have to make my sweaters a little longer overall to accommodate the stretching.) For women with broad shoulders, you might have to start with numbers for a smaller size and increase to the larger size after the waist shaping. But changes like this are infinitely easier to figure out than trying to alter the shoulder region of a sweater.
So there you have it! My cowl pattern is written, I’ve chosen a size (38”), I’ve cast on. Next up: Detours from The Plan.