Sweater knitting and suit shopping have something in common: If a sweater doesn’t fit your shoulders, it will never ever look good. But sweater patterns are sized by the bust, not the shoulders. So how do you ensure a proper fit?

The answer begins with understanding why sweaters are sized by the bust. It actually couldn’t be any other way, because for many constructions it’s unclear what the “shoulder” measurement might be. Set-in sleeves (contiguous or traditional) could size by the distance from sleeve seam to sleeve seam (also known as the sweater’s “cross chest”)…

…but what about yokes? raglans? Sideways all-in-one piece?

Every sweater construction has a bust circumference, though. And here’s the thing:

No matter what your size, all hand knit sweater patterns are created for the same body shape. (Let’s call her “Miss Average”.) Designers use the Craft Yarn Council of America charts, or some close variation on them. The measurements in those charts depict the same shape woman, regardless of size.

Here’s the final kicker:

Miss Average’s bust is a good indicator of her shoulders.

Her bust and shoulders are tightly linked. So when a sweater fits her in the bust, it fits her in the shoulders as well, without any modifications required. This is not true for many, many women.

So how do you pick a size, if not by your bust, when patterns are sized by bust? The answer is your upper torso circumference:

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Your torso circumference is the “bust” measurement that closely matches your shoulders. So you should use your upper torso circumference, instead of your full bust, when choosing a “bust circumference” size.

For some women, this won’t make much difference. For busty women, you’ll be choosing a size smaller than your bust (sometimes by a fair amount). For broad-shouldered, smaller-busted women, you’ll be choosing a size larger than your bust. When choosing a size, you have three basic fit options. Let’s look at an example of each, on my frame. For reference, my upper torso circumference is 38” and my full bust is 41”.

• A snug fit will fit fairly close to your body. The armholes will be a bit smaller, and the shoulder fit more figure-conscious. Achieve it by selecting a bust size 0 – 1” larger than your upper torso circumference. Here’s what it looks like, in a sweater:

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  (This sweater is a size 38”, exactly matching my 38” torso circumference.)

• An average fit is just that: Average. It’s comfortable, will fit your shoulders but not super-tightly. Achieve it by selecting a bust size 1 – 2” larger than your upper torso circumference. Here’s what it looks like, in a sweater:

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  (This sweater is a size 39.5”, 1.5” larger than my torso circumference.)

• A relaxed fit will still fit (the shoulder seams won’t be down on your arms), but it will give you plenty of space in the armholes and chest for a few layers. Achieve it by selecting a bust size 2 – 3” larger than your upper torso circumference. Here’s what it looks like, in a sweater:

  /i2.wp.com/www.amyherzogdesigns.com/wordpress/wp-content/uploads/2013/07/3948983162_dc567ac2a4_o.jpg?resize=198%2C300" target="_blank">https://i2.wp.com/www.amyherzogdesigns.com/wordpre...67ac2a4_o.jpg?resize=198%2C300 198w, https://i2.wp.com/www.amyherzogdesigns.com/wordpre...67ac2a4_o.jpg?resize=133%2C200 133w" width="232" />

  (This sweater is a size 40.5”, 2.5” larger than my torso circumference.)

To get a great fit in your shoulders, here’s how to select a sweater size:

1. First, take your own upper torso circumference. Place the measuring tape as high in your armpit as it will go, pull it pretty snugly, put your arms to your side, and breathe normally.
2. Next, decide on the fit you want. Average? Snug? Relaxed? Add the appropriate amount of ease to your upper torso circumference.
3. Look at the finished bust circumferences of the pattern. Find the one closest to your result from Step 2. This is your base size.
4. Compare the other measurements for that base size against your own body to determine what modifications you’ll need to make. For example, if everything works aside from the full bust vs. your own full bust (because you’re a busty figure), you will add an inch or more of bust darts to the front of the sweater. If everything works aside from the hip, because you have larger or smaller hips, that’s an adjustment you can make to the cast-on stitches. And so on.

And there you have it! If you choose your sweater size in this way, you’ll achieve a great fit in the shoulders, and be well on your way to a fantastically-fitting sweater. You might need to make some modifications, but by and large it’s far easier to tweak the waist and hip fit, rather than to try and fix shoulders that are fundamentally wrong.

How close in size are your favorite sweaters to your upper torso circumference? Had any sweater disasters? Let’s talk in the comments! And happy Friday!