how to do a small bust adjustment (SBA)

April 3rd, 2012

It’s a little unfair that small bust adjustments don’t get talked about as often as Full Bust Adjustments (FBA) – they’re just as easy and just as not-scary. hehehe

Much like the FBA tutorial we covered  this morning – small bust adjustments (SBA) are nothing to be afraid of. Before we start lets ask some of the same questions:

Most patterns are drafted on a B cup – so if you are smaller than a B cup you may end up having trouble fitting patterns. You’ll probably need to alter your pattern to get the right fit over your bust – when we’re talking about reducing the bust of a pattern that’s called a small bust adjustment.

How do you know if you need to do an SBA on your pattern?

Easy! You know that nifty size chart you get on the back of your pattern envelope? If you find that your bust measurement falls in a smaller size column than the rest of your body – then you’ll probably need to do one. If you’ve already made a muslin, you might notice you need to do an SBA because things just aren’t quite right in that area. Some symptoms may include

  • excess fabric and sagging around the bust area (oh dear!)
  • the bodice of your dress being too large around your bust, even though it fits perfectly over the rest of your body
  • the dart apex hitting you too low
Ok cool. So now we know if we need one. Shall we begin the alteration?
Calculating the size of your SBA is similar to what we did this morning for FBA. It’s easy as pie. Just figure out what size you would be if you used your bust measurement – then compare it to what size you would be if you used your other measurements to determine your size. On the bodice front of the pattern, measure the distance between these sizes. This is your SBA amount! We will be reducing the bust by that much.
Now the fun part. Lets draw some crazy lines all over our patterns. Kidding. They’re not crazy, they have very specific purposes.
  1. First extend the dart apex along the centre fold line by 1 inch. (we’ll call this line 1) This should be your centre bust. Mark this point.
  2. Next draw a line from this point to your armsyce, about 1/3 of the way in. (this is line 2) Conveniently, the circular markers on the armsyce are pretty much 1/3 of the way up.
  3. Draw a line down from your centre bust straight down – alone the grainline. This line should be parallel to the fold guide lines on your placket front (line 3)
  4. Draw a line perpendicular to grainline about 1/2 way down the placket (it doesn’t matter too much where you draw this line, just don’t go too high and interfere with your dart). This line (4) should hit the Line 3 and edge of the pattern
The basic idea is that we’re going to slash along these lines to overlap our pattern to remove the extra room we don’t need.
Cut Line 3 from the bottom to the centre bust, then along Line 2 armsyce, making sure not to cut completely through the pattern paper at the armsyce. We need to leave a little bit so that we can use it as a hinge.
Next cut Line 1 from the side seam towards the centre bust. Do not cut completely through the pattern paper at the center bust. Once again, we want to leave a bit of paper to use as a hinge.
Now we want to overlap the slashlines by the amount of our SBA. Keep them parallel along the grainline.
Next we need to slash along line 4 – since the centre of the bodice is now a little long. Overlap it so that the waistline matches up with the side we just completed.
Tape everything in place
Redraw the dart lines, then trim the excess paper on the edge.
And we’re done!!
Things to note:
  • This adjustment will change the size of the waistline (ie make it smaller) so you may need to make an adjustment at the waistline to maintain your correct size
  • You might not need to do a bust adjustment at all! You lucky B cup you :)
  • If you have the opposite problem and need to do a Full Bust Adjustment instead – then checkout this tutorial

20 Responses

  1. [...] I know what you smaller than B cup ladies are thinking right now – umm what about me?? Don’t worry, we’ll be back this afternoon to tackle Small Bust Adjustments! [...]

  2. Shona says:

    Thanks for covering this! I haven’t been doing SBAs but I know I should. I usually just take in at the side seams but this looks like it would work better. Thanks for not forgetting about us smaller cup ladies! Our fit issues do get overlooked so often in the sewing world (and the real world for that matter).

    • Meg says:

      You’re so welcome Shona! It really is unfair how often fit issues for smaller ladies get overlooked :) I’ve had to do this one a couple of times for family members, so I knew i didn’t want to leave it out of the sewalong :)
      Best of luck with trying one in the future!
      XOXO

  3. Brilliant! I need to practice my sewing skills more :) Your inspiring!

  4. Jennifer says:

    Hi, I think I’m slightly confused: my chest measurement is a size smaller than the hip/waist measurements in pattern size guides. But I’m a C cup in bra size so I haven’t really considered that I’d need a SBA before… At any rate, I’m looking forward to the sew along!

  5. Shona says:

    I’m working on mine right now and just want to make sure I understand. So I’m cutting an XS in the top and a S for the bottom. My bust is 31″ compared to the 33″ on the pattern. Does this mean I need to take 2″ out of the dart? I was thinking since there are 2 darts, wouldn’t that reduce the bust by 4″ instead of 2″? Or should I do 1″ on both sides?

    • Meg says:

      Shona you are totally right! You’d want to divide that number by 2 – so you’d reduce each side by 1″. Sorry that wasn’t clear in the tutorial!

      • Katy says:

        Meg – wouldn’t this be 1/2 inch rather than 1 inch? The envelope measurements are for the whole circumference of the bust whereas the pattern piece is one quarter of that? By the way have the bust sizes changed on the pattern envelope? Shona says an XS is 33″ on hers but on mine an XS is 34″. Anyway I’m having a go at my first SBA – thanks for the tutorial!

        • Meg says:

          Hi Katy!
          Thanks for the questions! In this instance it wouldn’t be a quarter of the whole circumference since we are only altering the pattern front, not the back as well. So the difference is divided only across the front of the pattern (ie by 2). If we were adjusting the back too then we would divide by 4 :) I hope that helps!

          Meanwhile, with respect to the pattern sizing – the sizing hasn’t changed, but the way that it’s stated on the pattern envelope/instruction booklet has changed. We used to state our sizes as a range ie, XS was 33-34″, S was 35-36″ etc. But we found that was confusing for people, and didn’t leave enough room on the back of hte envelope for including metric measurements too. So now we just state the upper limit of the sizing. So XS is stated as 34″ (ie up to 34″) and S as 36″ (ie more than 34″ but less than 36″). I hope that helps!!

          Good luck with your SBA! I know it seems daunting at first, but you can do it!!!

          Hugs. XOXO

  6. Marina says:

    Hi Megan. Thanks for the speedy service on my order! I’ve finished my first dress and love it. Such a fabulous pattern which I highly recommend.

    Can I ask a question about the dart? The angle of the dart is wider than other bodice patterns I’ve used and when sewn up created quite a “pointy” look in the bust. The apex also rests at the side of the bust rather than the front. I have an average bust and the size I chose (small) fits me perfectly in every other way.

    I’d like to make a smaller angled, longer dart but think that it will affect the length of the bodice. If I do that, can I just adjust the bottom edge of the bodice afterwards to match? Hope this makes sense?!!

    Thanks so much….

    Marina.

  7. Marina says:

    Me again, sorry, in my last comment I meant to ask in the last sentence “Can I adjust the bottom edge of the front bodice afterwards so that it matches the length of the back bodice?”

    M.

  8. Diane Drexel says:

    Hi Megan,
    When I redraw the dart, do I redrawing it the same size as the original pattern or am I also adjusting the amount there as well? If I am adjusting it, how do I know how much?
    Thanks,
    Diane Drexel

  9. River says:

    Can any one point me in the direction of advice on how to take in a shop bought item? I guess I need to put a dart in but I’m not sure where exactly, the excess fabric doesn’t seem to be where the existing dart is.

    Google has not been much help, results are what styles to choose and enhancement techniques.

    Great article. Has insired me to try and make my own next time…

  10. [...] irriterande på ett för övrigt löst sittande plagg. Läxan är väl att man bör göra en riktig anpassning för en liten byst, som inte påverkar axlarna. Ett annat litet irritationsmoment är att ärmarna blev lite för [...]

  11. Angie says:

    Hi! What if you don’t want to shorten the bodice or loose room at the waist and hip? I’m doing a 1/2 inch sba. It’s resulting in a 1/2 inch loss at the waist and hip. Also I’m losing about 5/8″ in bodice length and my armsye is bigger slightly due to the shift there. I haven’t cut out my fabric yet, but I did add back in the length on the side seam at the bottom and slightly at the under arm the total amount lost in the sba. Does this sound reasonable? But I’m uncomfortable with how to add it back at waist and hip. Also I redrew my darts at same size as original otherwise the sba would not have made much of an impact – right?

  12. Meghan says:

    So I’ve been reading small bust tutorials for the last year. I’ve read Colette’s, Gertie’s, and other blog posts on tissue fitting and flat pattern adjustments.

    THIS IS HONESTLY THE ONLY ONE THAT HASN’T MADE IT SEEM CRAZY COMPLICATED.

    For the first time I’m thinking, “Oh. Hey. Maybe it is time to sew that dress that I know needs some dart adjustments.”

    Thank you so much for posting this. :)

    P.S. I’m totally in love with your latest pattern collection. Trying to decide what to make first is so hard!!

  13. Lili says:

    Hei, I have a top that has two darts around my bust and then the top ended up to be too big for me, I wont be able to cut as you do on your pattern, but I understand that from small to bigger size the darts move more open to the side of your body. So I wonder if I just have to move the darts more inside and the excess sew it in??. Its very difficult to explain :( I jope you can understand me.

  14. Etta says:

    What if you need to go smaller than the lines in the pattern? Any tips for that?

  15. Carly says:

    Hi there!
    I really want to make this pattern, but I have a much smaller bust, a 30-32″ :( How can I adjust the pattern for a SBA now that the digital pattern (purchased May 2014) has been altered to have a waist dart instead of a bust dart?

    If anyone can help, I’d be so grateful, it’s totally confusing me how to do it!

    Many thanks :)