I’ve had a lot of requests for tutorials for doing a full bust adjustment (FBA) and small bust adjustment (SBA) for the Banksia pattern, so I wanted to make sure we had a tutorial on how to do them on this pattern, specifically.
Wait, what is a bust adjustment? Most patterns are drafted on a B cup – so if you are significantly larger or 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. When you need to add room to the bust of a pattern, thats called a full bust adjustment.
I’ll first show you how to measure and prepare for both type of adjustments, because those first few steps are the same. And then we’ll delve into FBA and then SBA.
Ok, let’s go.
DETERMINE IF YOU NEED ONE
Before we get started, let’s discuss how to determine if you need a FBA or SBA. You know that handy size chart you get on the back of your pattern envelope? If your bust measurement falls in a different size category than the rest of your measurements, then you most like need to do a bust adjustment. 
Knowing your measurements is a sure way to know if you need an adjustment. But if you’ve already done a muslin and it just isn’t fitting right, some of the signs you may need a FBA are:
- the waistline being higher at the front than the back of your bodice
- the fabric pulling around your armsyce
- 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
Some signs of a poor fitting muslin that may indicate the need of a SBA:
- excess fabric and sagging around the bust area
- 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
CALCULATE YOUR FBA OR SBA
So now you need to use these signs and measurements to figure out how much your adjustment should be. An easy way to do that is 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 how big your FBA or SBA will be!
For example:
If you are a Small based on your waist and hip measurements, but a Medium based on your bust measurement, then you would measure the difference between size Small and the Medium. Let’s say its 1″ (just for example. make sure you measure yourself). Then you would cut the Small, and do a 1″ FBA.
If you are a Small based on your waist and hip measurements, but an X-Small based on your bust measurement, then you would measure the difference between size Small and X-Small. Let’s say its 1/2″ (just for example. make sure you measure yourself). Then you would cut the Small, and do a 1/2″ SBA.
Whew, ok! I know that seems like a lot, but I swear it isn’t. And now you can get to work!
To prepare your pattern piece for either adjustment, you’ll need to draw 4 lines. I’ve numbered them in different colors so you can see what I am talking about.
- 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 that point.
- Next draw a line from this point, your centre bust, to your armsyce, about 1/3 of the way in. (this is line 2). Conveniently, the notch on the armsyce of this pattern is about 1/3 of the way in.
- Draw a line down from your centre bust straight down to the bottom of the pattern – along the grainline. This line should be parallel to the centre front fold line (line 3).
- Draw a line perpendicular to the 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.
Now we are going to slash along these lines. 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.
From here we can now add room for a FBA or remove bulk for a SBA.
For a FBA, you will 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″. This will also open up your dart wider, because it is on that hinge you left. Place paper underneath and tape in place above line 4.
Now you need to fix the waistline. The centre front should now be 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. Place another small piece of paper under there if you need to, and tape the rest in place.
Re-draw your dart legs and your new centre dart fold line.
Then fold the dart downwards as if you are “making the dart”. Cut along the side seam to true it, and you’re done! Admire your new fuller bust dart.
Note: using this method will also increase the waistline width of your blouse by the same amount of your bust adjustment (in this case by 1”). But since it is already a loose fitting blouse, we’ll just keep it as is.
So for a SBA, you’ll be using the same slash lines, but you will be overlapping instead of spreading.
Overlap the pieces of slash line 3 by the amount of our SBA – for this example I used 1/2”. Keep them parallel along the grainline. As you can see, this will also cause your dart to overlap and therefore become smaller.
Now you need to fix the waistline. The centre front should now be slightly longer. Cut along line 4, cutting completely through – then move it up, overlapping till it is in line with the new waistline. I like to use my ruler to keep it straight.
Tape everything in place.
Redraw the dart lines (note – my bottom dart leg was hidden under the overlap), then trim the excess paper on the edge.
Ta-da!
So like I mentioned with the FBA, using this method will also decrease the width of the waistline by the same amount of your bust adjustment (in this case by 1/2”). But since it is already a loose fitting blouse, it doesn’t matter too much.
BUUUUT if you do feel you need to make an adjustment at the waistline to maintain your correct size, you can do it like the photo above. Just add the missing amount to the bottom edge, and draw a new side seam line up to the bottom of the dart leg.
