how to do a full bust adjustment (FBA)

I kind of feel like the first thing i want to say is…



Something i hear over and over from people is their trepidation about pattern alterations. Especially bust adjustments – they seem so mysterious and potentially complicated. But they’re not! Please don’t worry, it’s not beyond your ability! Honest.

So, what is a full bust adjustment (FBA) ?

Here’s the deal. Most patterns are drafted on a B cup. I know that’s probably upsetting those of you who aren’t B cups, but the unfortunate truth is that patterns need to drafted in some sort of base standard. What does this mean for people who aren’t B cups? Well, you’ll probably need to alter your pattern to get the right fit over your bust.

How do you know if you need to do an FBA 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 larger 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 FBA because things just aren’t quite right in that area. Some symptoms may include

  • the waistline being higher at the front than the back of your bodice
  • the fabric pulling around your arm syce
  • an inability to close the bodice of your dress around your bust, even though you can over the rest of your body
  • the dart apex hitting you too high
Ok cool. So now we know if we need one. Shall we begin the alteration?
Calculate how large your bust adjustment should be. This too, is not scary. Just figure out what size you would be if you used your bust measurement – then compared 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 how big your FBA will be!
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 spread our pattern out to make room for the extra bustyness.
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.
Spread the centre slash line (line 3) by the size of your bust adjustment. Make sure you keep the slash lines parallel (ie keep the distance the same all the way down). For this example i’m going to use an adjustment of 1″ (i know in the picture above the gap isn’t 1″ yet)
Now we need to fix the waistline. The centre front is now slightly shorter. Cut along line 4, cutting completely through – then move it down till it is in line with the new waistline. I like to use my ruler to keep it straight.
Put some pattern paper underneath, and tape everything together!! The last thing we need to do is true the seams along the dart line.
Draw the new dart legs and centre fold line.
Then fold the dart downwards as if you are “making the dart”.
Cut along the side seam – and you’re done!
Things to note:
  • This adjustment will change the size of the waistline (ie make it wider) so you may need to make an adjustment at the waistline to maintain your correct size
  • 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!

Never miss a post!

Enter your email address to receive our posts right to your inbox

Featured Products

Megan Nielsen Fabric stash note cards Megan Nielsen Briar sweater and tee sewing pattern Megan Nielsen Yes I Sew, No i won't do your mending tote bag


    • MegMeg says

      Yep i did! That’s the unfortunate side effect of this adjustment -it increases the waist too. I admit, at first glance it does seem a bit weird.

      Basically the reason is that we need to maintain the grainline of the original pattern so that the bodice still sits correctly. The way i would deal with the larger waist is to remove the excess from the side seams.
      This is one of the reasons i’m really grateful i don’t tend to need to do these adjustments on myself, and to be honest I think I would approach the issue a little differently than the standard method shown above- but since I had so many requests for this adjustment i figured it was important to include :)

      Meanwhile, your comment made me realise i really should have mentioned this in the post! perhaps i’ll update it now :) Actually I think I may add another post with some other ideas for adjustment.

      • Kez says

        so, just so that I am clear…are you saying that to make the waist smaller again, I just make the seam allowance at the waste larger? Does this mean that I should figure out how big the waist would be BEFORE slashing into the pattern, or will it be easy to figure out?
        (sorry, beginning sewer here, but I am DETERMINED to make this dress!)

        • MegMeg says

          Hi Kez! No worries i understand :)
          Basically what you’re doing is increasing the bust and waist by the same number (lets say it’s 1″ like our example above). That means that your waistline will be 1″ bigger. So you’ll want to draw a point 1″ in from the side seam at the waistline, and draw a line to join that point to where your dart meets the side seam. Then cut along that line and you’ve got your new side seam :)
          It should be obvious how much you need to remove since it will be the same amount you added to the bust. Does that make sense? XOXO

  1. Kelly says

    That’s so neat. I’m nowhere near being able to make a dress – I’m more the…making a handkerchief experience range :-) But I was thinking while reading your blog how I see so many nice dresses like yours that end up looking empire waist on me because they don’t fall right. Great to know that there is a way to adjust that!

    • MegMeg says

      I’m so glad to hear that!!
      You know what you might also consider? My sister in law has a similar issue where dresses are always realllly high waisted on her – and after we compared our proportions we realised she just has a long abdomen! Perhaps it’s the same thing for you? If you think that might be it we’re also doing a tutorial for lower the waistline of this dress this week :)

      • Kelly says

        That’s a great tutorial too! For me though it’s definitely the bust issue – I’m 5’2 and a D – although lucky for her to have a long abdomen – I guess we all want what we don’t have! :-) Thanks again for all you share here.

  2. says

    I’m still a bit unsure if I need to do an FBA. I’m in between a B and a C cup. My measurements are 44,40,47. I graded the pattern accordingly and I still had high darts. Should I do an FBA as well?

    Thanks in advance!

    • MegMeg says

      Hi Melizza!
      Yeah i totally understand what you mean!
      Reading what you’re saying – I’m wondering if perhaps you need to actually simply lower the dart, rather than doing an FBA? It sounds like your cup size might not be the issue if you’re between a B and C.
      The dart has been high on some people – If i was you i think i’d try shifting the dart downwards.
      I hope that helps a bit!! XOXO

      • says

        Wonderful! That is what I had guessed and it’s the last adjustment I made to the pattern. Phew. Glad I don’t have to do any further changes.

        Thanks so much for getting back to me. Even though my last wearable muslin wasn’t perfect I wear it all.the.time. I cannot wait to make a few better fitting ones.

  3. Marie says

    Hi Megan,
    I just received the pattern(s) and couldn’t be happier. So much so that I have already read the instruction booklet several times !
    One thing I have not seen, though: are the seam allowances already on the pattern? If yes, the darts are too high on me and I will have to lower them.
    But if not, I will have less prep work to do :-)
    I am so looking forward to sewing along with everyone!

    • MegMeg says

      Hi Marie! Yes the seam allowances are all already included, and they are 5/8″.
      Given what you’ve said it sounds like the darts will be a bit high on you and might require some lowering :)

  4. Debby says

    My daughter does not have a full bust, but she does have an extra small waist. I tried to grade the pattern from small at the bust to extra small at the waist, but I had some problems with that. there seems to be a lot of extra fabric in the bust area. Maybe she needs a straight xs for bust and waist? She measures 33.5, 25, 37 (if I remember correctly). Any suggestions?


  5. Clarissa says

    Wow! Megan, this is the best picture tutorial I’ve ever seen for an FBA. Can’t wait to get started!!!

  6. Clarissa says

    Was just reading some other comments. I think I need to lower my dart. How would I go about doing this?

    • MegMeg says

      Ooo I didn’t see this one before! Lowering the dart is pretty simple – you just need to cut it out or slash about it, and move it down making sure you keep it in line with it’s original position. Then you’ll need to redraw the side seam. Tomorrow I”ll be posting about how to lengthen the bodice by slashing under the dart – perhaps something similar slashing above the dart would work well for you.

  7. says

    So in my muslining of the Darling Ranges dress I am having serious issues with that dart. It is already a big honking dart as drafted and once you do a FBA it is HUGE. It looks so pointy and unflattering when sewn up; any ideas on ways to address this?

    • MegMeg says

      Hi Julia! I’m sorry to hear you don’t like the dart! If you’re finding it too large then I’d say it’s very unlikely you need to do an FBA – if it is pointy then (as counter-intuitive as it may sound) you may in actual fact need to reduce the bulk of it by doing something similar to a small bust adjustment
      Perhaps then you’ll find a shape that you prefer :) Otherwise, you could try spreading it out over 2 darts – one at the bust and one at the waist? Or even eliminating it completely if that is a style you prefer.
      I hope that helps a bit!

      • francesca says

        Hi Meghan
        Any ideas on the issue of distance between the darts in front? I have made another muslin in a larger size and still have the same problem:(

  8. says

    so I have a weird question. I went ahead and worked on my fba and lowered the dart. I thought I did the math correctly but when I moved on to a muslin for the bodice my dart is pointing out away from my body and I have a ton of fabric in front of it (does that make sense?). I just retraced the pattern to go back to the original pattern and I noticed that the original dart does this to me on the tissue, but I have no idea what this means. the rest of my muslin looked perfect (the armhole fit great, the fronts met, and the back couldn’t be more perfect, I even lengthened the fronts a bit knowing I would need this) but I don’t know how to fix this. do I need another dart? or a differently shaped dart?

    • says

      I’ve encountered the same problem. It’s like the fabric is pooling at the tip of the dart. I tried shortening and lengthening it, same problem each time. I didn’t need to lower or raise the dart (although I did try in in my previous muslins just to be sure).

      I thought about reshaping the dart, but honestly, I’ve never had to deal with a dart this wide before. Perhaps I may split it in two and move one to the waist. But by doing that, I would be on Muslin #7.

      It’s annoying because the rest of the bodice fits just fine except for the dart.

      Sigh. This dart has become the bane of my existence.

  9. Francesca says

    love the pattern, and plan to get Banksia too if it works out… I too am having problems with the dart positioning. I don’t need an FBA or an SBA as far as I can see – but although the points are at the right height the darts are kind of too wide for me, if that makes sense. I seem to havetoo much space between them. Of course, I realise that they shouldn’t finish on the point of the breast – I’m quite an experienced sewer – but they look wierd on my muslin. could it be that I need to lengthen my darts?

  10. Megan says

    This is awesome, thank you! So far the darts are the only thing I will change for the next time I make this dress, as they don’t end quite where my boobs do. I am also a lucky between B and C cup person, so it’ll take some fiddling but I think it’ll be worth it. This is so helpful!

  11. Val Poole says

    Hi Megan, I have just read your instructions for changing the pattern for a full bust. My query is – my pattern has the dart cut out already as in an upside down V and then I have to line it up with the circles on the pattern. My bust is 7cm lower than the bust apex in the pattern, and I am full busted. I have been trying to fathom out how to go about changing the apex, and increasing the bust to fit me. Do you have any ideas? Hope you can help, best wishes Val.

  12. says

    Is it possible to do some sort of a FBA on a pattern without a dart? I’m making your eucalypt tank pattern for my daughter who is a D cup. I’m afraid if I make the size that will fit her bust, everything else will look too big (armhole, drape of tank around the body/waist).

  13. Asha says


    I have recently purchased the darling ranges pattern and am getting ready to make it but i need to do a fba, however I think the pattern has been updated since this tutorial as there is now a waist dart instead of a bust dart, I have no idea now to do the adjustment :o(

    I hope you can help


  14. Rachel says

    Hi, I’m having the same issue as Asha – need to do a fba but don’t know how to deal with the waist dart!


  1. […] want to get that Sorbetto right after all, and so I pulled out my patterns, my tracing paper, and some instructions, and went to town on that FBA. I had made a size 14 before, but this time I cut out a 10, made a […]