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Using upper chest to pick a better size

Updated: May 24

There's a lot of talk in the industry about the upper chest measurement. Here's what you, as a knitter, need to know.

What's the upper chest measurement, anyway?

The upper chest measurement is taken across the chest over the breasts, at a diagonal angle under the arms, and flat across the back.

A woman stands in her undergarments. a dashed line runs across the full bust. A second line runs from under the arm, above the breasts and across the chest. This is where the upper bust is measured.
Upper chest is a better measure of frame size.

Why does this measurement matter?

Everything I need to tell you about your upper chest measurement flows from one fact - sweaters need to fit your frame, and bust size is only weakly correlated with your frame size.

When we fit garments, it's important to fit from the top down. Because garments hang from the shoulders, then down through the underarms and across the top of the torso before even reaching the underarms, it's important to fit those measurements first.

Note: Check out the illustration - that full bust line? It's in the lower torso. We're so used to thinking about our busts as being at the underarm because in knitting, we usually reach the full bust stitch count at the underarm. But it's not - it's beneath the underarms. It's a lower torso measurement.

Instead of asking knitters to choose a size based on their underarm depth (armscye), shoulder width, and neck width, we can instead look at upper chest. Upper chest is a good predictor of those measurements because it measures the torso size. It's also a heck of a lot easier to measure your body's circumference there than it is to accurately measure your shoulder width and armscye without help!

Put another way, sweater fit depends on your armhole depth, shoulder-to-shoulder width, neck width, ribcage circumference, and full bust - and full bust is the least critical and easiest to adjust. It's also a poor indicator of what the other, more critical, measurements will be. The other numbers all travel in a pack without a lot of variation - if you tell me your upper bust, I can probably guess pretty close to your shoulder width. But if you tell me your bust circumference, I would have a very difficult time. So why are we all picking our sweaters based on our full bust? That's like choosing a bra based on cup size alone!

Here's a quick visualization if that's not clicking - at the end of the day, we take off our bras, and our full bust measurement instantly changes. But we have not changed size!