Monday, November 2, 2015

1940's Bra Sew-Along - Adjusting Bra Cups

It's time to talk about the bra cups! At this point you'll have chosen your size and sewn your muslin (don't worry, no deadline! I'm just posting this now per request). Some of you will find that the bra fits pretty well on the first try (lucky you!).

Here is how the pieces are meant to rest on your figure.

Others will find that they need more or less room in the cup area. That means we need to make adjustments to the seam between pieces A and B.

Above is the seam we're looking at highlighted in blue. For reference, the top of piece A should be about 7" from where a shoulder seam would sit on a t-shirt. The pattern doesn't use cups sizes, as we discussed earlier, but that doesn't mean we can't make cup adjustments. For our purposes, it's a good idea to only adjust cup size one size at a time. This pattern is approximately a B cup depth-wise, and the increase (or decrease) rate is 1/2" per cup.
Warning: adjusting the cups beyond a DD can really change the shape of the bra and it might not look the same after. I'm talking about uni-boob, a very real threat.

This is how you will need to add or subtract allowance from the seam:

Due to the shape of these pattern pieces, I recommend adding the brunt of your changes to the seam on piece B. First trace your pattern pieces onto a new sheet of paper (leave some room around them to make adjustments. To increase the cup size, add 3/8" to uppermost curve on piece B. Add 1/8" to piece A. This will equal 1/2" in total.

Note: If your girls tend to rest more to the side than front and center (some of us carry more fullness an inch or two nearer to the side), then you can shift the added bit to sit closer to your fullest point.

From this added bit, you'll want to smooth the new line to nothing until it blends to touch the side and center front seams at the ends, as illustrated above.
As you add this change, you want to make sure that the seam edges on the left of this diagram stay the same height. These still need to match up to piece D later on.

Now, by adding allowance to this seam, you're actually lengthening the seam line and piece B won't quite match piece A any more. This can be fixed by walking the pattern pieces together to match them up. Measure the difference between the pattern pieces and then add the difference to piece A as illustrated above in pink. If you make any changes to the sides of piece B, keep in mind that it still needs to match up with piece C.

Do the same to remove too much room at the cup seam by subtracting rather than adding the 1/2".

And just like that, you've adjusted your cups! Now it's time to test it again in muslin to see if that sucker fits better.

Happy sewing,


  1. Do you have any suggestions for adjusting to beyond a DD, or is it simply not feasible with this style/pattern? Thanks!

    1. Hi Angie, I would suggest tying it in muslin and seeing if it works for you. To a certain extent, each pattern reaches a point when sized up where it no longer resembles the original pattern any more. That said, there is nothing to say it still won't be an attractive bra, it just might take some tweaking.

  2. 3rd time is the charm! Had to adjust cups a couple times, and placement of extra fabric. Finally have a fit I'm happy with - now to start the actual fabric?

  3. This is so much fun and am i ever learning a lot about adjusting fit:). So far ive made 2 mock with original pattern and sized up as you directed...the other i have to alter the pattern as i think im beyond what the original can hold. With the original im finding i cant get that shape as sharp and 'perky' as i would like and im not sure if i should reinforce the cup seams or have sharpened up the curves when i adjusted the cup size... im a littled delayed, sorry. would you have any suggestions?

  4. Do you have any patterns for a triangle bra?

  5. Hey thanks for the tutorial :)) I used your picture as a reference to draft my own mockup cups!