May 28, 2015 :: by Jerusha Robinson
Working out the math for Kathryn was almost as fun as the knitting itself…here's how I did it:
Step 1: Know your parameters
As I mentioned earlier, I didn’t want a straight tee, I wanted my sweater to have an A-line shape. I have a favorite cotton tee that is snug in the shoulders and bust, and swingy at the hem. (Also striped, of course! I've found that I can never have too many striped garments.) Here it is:
From my tee, I took measurements (see the schematic below).
Step 2: Know your gauge and do some math
In my gauge swatch, I get 25½ stitches and 32 rounds over 4", or 6.375 stitches and 8 rounds per inch. To figure out stitches and rounds, I can go down my list of measurements and multiply the number of inches for each measurement by my stitches per inch (for widths) and rounds per inch (for lengths). For example, the bust for my sweater is going to be 36" around.
6.375 (my stitches per inch) x 36 (my bust measurement) = 229.5, or 230 stitches, rounded up, so I need to make sure I have 230 stitches at the bust of my tee.
And, my yoke is going to be 7¼" deep, so 8 (my rounds per inch) x 7¼ (my yoke depth) = 58, so I need to knit 58 rounds to reach my yoke depth: the place where I separate front and back from sleeves.
Two more very important stitch counts to figure out here: The total number of stitches to get to before separating the body from the sleeves, and the number of stitches to cast back on at the underarms, when separating sleeves from front and back. I invoked the EPS (Elizabeth [Zimmermann]'s percentage system) here, no need to re-invent the wheel—and please note that I used Meg Swansen's updated version from the Opinionated Knitter.
Based on the total number of stitches I want at the bust (230), I used the percentage system to determine how many stitches I want to cast back on at the underarms after the separation of body from sleeves (12). After subtracting that number from the bust twice (one for each underarm!) and from each sleeve, I added the remaining stitches together.
So, 230 – (12x2, or 24) = 206 body stitches,
and 72 – 12 = 60 (times two for the two sleeves), or 120 sleeve stitches.
A grand total of 326 stitches are needed at the point where I'm ready to separate the body and sleeves (58 rounds).
Step 3: Knitting by the numbers
The original pattern calls for knitting from the bottom up. But I wanted a top-down pullover. So I started at the neck.
Now comes the tricky part…figuring out how to get from point A (neck circumference, 122 stitches) to point B (separation of body and sleeves, 326 stitches) to point C (hem circumference, 266 stitches).
Starting at the neck and checking the schematic and the math we've already done, we know that the yoke needs 58 rounds.
Next, I know I need to get from 122 to 326 stitches. To make things easy, I go back to the EPS. I want to achieve this over 4 increase rounds, so I calculate the number of stitches I need to increase for each of those rounds. For a deeper yoke than mine, consider doing more increase rounds.
Using the percentage system, I've determined that I want to increase 61 stitches in the first increase round, 45 stitches in the second and third increase rounds, and 53 stitches in the fourth increase round.
I have two more tasks for this section: How to space these increases evenly across each increase round, and how to space the increase rounds vertically over the yoke depth.
There are great resources out there for making the first of these calculations; I’ve listed some below (see end of post). The one I landed on was from a past issue of Cast On magazine. I divided the number of stitches I have on my needles by the number of stitches I needed to increase. Of course, it doesn't always work out perfectly. But for my first increase round, it does: 122 / 61 = 2. This means that increases need to happen at 2-stitch intervals this round. And because I don't want to be increasing at the very beginning or end of my round (might look weird with the changing colors), I took one of those intervals and split it between the beginning and end of the round. So! My first increase round looks like this:
K1, (m1, k2) to last stitch, m1, k1 (61 sts inc'd)—183 stitches.
The next one isn't quite so neat:
183 / 45 = 4.06666667, or 4 with a remainder of 3.
We can just tack that remainder onto the front of the round, no need to split it up. Here's what this looks like:
K3, (m1, k4) to last 4 sts, m1, k4.
And so on.
To figure out how many rounds to work between increase rounds, I took the total number of rounds in the yoke and divided it by 4 (one for each increase round). This means I have about 13 rounds between each increase round in the yoke.
I used this same method for figuring out how to get from bust stitches to hem. I begin with 230 stitches at the bust, and I need to get to 266 stitches at the hem. The total number of stitches to add is 36, and I want to increase 4 stitches every time I work a shaping round, two at each side:
36 / 4 = 9, so I need 9 increase rounds, spread over a length of 14½", or 116 rounds.
116 / 9 = 12 with a remainder of 8. So, I work my increases every 12 rounds, and have 8 rounds to go to achieve the body length.
For more information on spacing increases/decreases evenly in your knitting, see:
Next up: The knitting!