How to adjust the side seam angle of a bra

Bodies (and boobs!) come in all shapes and sizes, and you may find that you need to adjust the side seam angle of a bra to achieve a better fit. Today, we’re showing you how to do just that!

Jump to another post in this series:

1. Bra fitting guide overview
2. How to choose your bra size
3. How to make a test bra
4. How to adjust the back band
5. How to adjust the gore/bridge
6. How to adjust the cups
7. How  to adjust the center insert
8. How to adjust the side seam angle
9. How to adjust the straps
10. How to adjust the underwires
11. Adjusting the level of support and comfort
12. How to make an asymmetrical bra
13. Where to get bra making supplies
14. Additional bra making resources

Cashmerette has bra sewing patterns designed to support and lift big boobs in band sizes 28-54 and cups C-J, all while looking absolutely fabulous (It’s a lot to ask of a bra, but they are up to the task!)

In this post, we’re covering how to adjust the side seam of a bra to achieve a better fit. Let’s get started!

How to tell if you need to adjust the side seam

Our bodies come in many different shapes, and the angles of our side bodies vary significantly.

Put on your muslin (test version) and take a look at how the underarm elastic sits on your body. Is it gaping? Is it cutting in? Are there wrinkles in the bra band at the side seam?  These may mean that you need to adjust the side seam angle.

How to adjust the angle of the side seam

For the Willowdale and Symmes Bras:

If your bra feels too tight under the arms, you can extend the length of the side seam by adjusting the angle of the seam between the front band and back band as shown by the red line below. Add half of the additional width you need to the front band and the other half to the back band, taper to nothing at the lower and inner edges of the pattern pieces.

Alternately, if the bra is too loose under the arms you can adjust the side seams inwards as shown in green.

Note: the length of the side seam should stay the same with either adjustment.

Once you’ve adjusted your pattern pieces, you’ll want to make another muslin and try it on to see if further adjustments are needed before you start your final bra.

For the Loftus Bralette:

If your bra feels too tight under the arms, you can extend the length of the side seam by adjusting the angle of the seam between the front band and back band as shown by the red line below. Add half of the additional width you need to the side cup piece and the other half to the back band, taper to nothing at the lower edges of the pattern pieces.

Alternately, if the bra is too loose under the arms you can adjust the side seams inwards as shown in green.

Note: the length of the side seam should stay the same with either adjustment.

Once you’ve adjusted your pattern pieces, you’ll want to make another muslin and try it on to see if further adjustments are needed before you start your final bra.

If you adjust the underarm seam, you will also need to take the same amount out of the length of underarm elastic that you use.

We hope this tutorial was helpful! Check out the full Cashmerette Bra Fitting Guide for more on sewing and fitting your dream bra.