I’ve had a lot of requests for tutorials for how to do a full bust adjustment (FBA) and small bust adjustment (SBA) for french darts like the one in my Dove Pattern, so I wanted to make sure we had a tutorial on how to do them on a french dart specifically!
The steps for doing an FBA or SBA on a French dart are very similar to a side seam bust dart, with a few extra considerations since French darts are constructed a bit differently.
So first things first – Let’s figuring how what a bust adjustment is and whether you even need one!
What is a bust adjustment
Most sewing patterns, including my 0-20 range are drafted on a B cup block and most Curve patterns like my Curve 14-30 range are drafted for a D cup. If your bust is significantly larger or smaller than the cup size a pattern is drafted for you may notice some fit issues when wearing and as a result need to adjust your pattern to better fit your bust.
When you need to add room to the bust of a pattern, that’s called a Full Bust Adjustment or FBA.
When we’re talking about reducing the bust of a pattern that’s called a Small 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 how to do an FBA and then SBA on a French darted pattern like my Dove blouse.
Determining if you need a bust adjustment
So how do you figure out if you need a bust adjustment? There are a couple of ways to find out!
Making a muslin
If you’ve already made a muslin using your full bust measurement to choose your size, but you notice fit issues like strange draglines or gaping around the armscye, the dart point hitting you too high, the waistline being much too high at the front compared to the back etc. then you may need a bust adjustment.
Checking the size chart
If looking at the size chart you notice that your full bust measurement is in a significantly different size bracket than your waist measurement. For example if your Bust measurements puts you at a 20 but your waist puts you at a 16 you might need an adjustment.
Comparing high bust to Full bust
Sewing cup size is determined by comparing the full bust measurement to the high bust measurement in inches. This may or may not correlate with your bra cup size which is calculated using your underbust measurement, so it’s worth measuring yourself rather than working off your expectations of your cup size.
Full bust – High bust = cup size
The number of inches between your full bust and high bust measurement will determine your cup size.
A cup = 1” difference
B cup = 2” difference
C cup = 3” difference
So in order to determine if you need an adjustment you can measure your high bust and compare it to your full bust. If the difference is significantly larger or smaller than the pattern is drafted for you’ll likely need to do an adjustment
Calculating the FBA and SBA amount
So now that you know whether you need to do a bust adjustment, we need to figure out how much of an adjustment to make and what size to cut out of the pattern!
There are two easy ways to calculate the size of your bust adjustment.
The first is using the high bust measurement. After measuring your high bust add on 2” (if using a pattern drafted for a B cup like Dove). We’ll call this your equivalent bust for purpose of explanation. Choose your pattern size based on this “equivalent bust” measurement. Your full bust adjustment less the calculated equivalent bust measurement is the amount of your FBA or SBA.
For example if your full bust measurement is 42” and your high bust measurement is 38”. Then your equivalent bust measurement would be 38” + 2” = 40”. This means you would cut out a size 14. The difference between your full bust and the equivalent bust is 2” so the amount of your bust adjustment is 2” total. We would then halve this number to determine the adjustment to the half pattern, and would adjust the front pattern piece by 1”.
The second method means comparing the different size bands of your body to the sizing chart. If your waist measures as a size 14 but your full bust measures at a size 16 then you would cut a size 14 and make your adjustments on that. The size of the adjustment would be the difference between the bust measurements of these two sizes. So in the example we have been using the difference between a size 14 and size 12 bust is 2”, so your total full bust adjustment would be 2”. We would then halve this number to determine the adjustment to the half pattern, and would adjust the front pattern piece by 1”.
You won’t necessarily get a bad fit choosing your pattern size on your full bust if you aren’t too far from the cup size drafted. For example I measure as an A cup, with a 1” difference between my high bust and full bust. However I never bother with an SBA as experience has taught me I can get away with choosing my size based on my full bust without noticeable fit issues.
Keep in mind that just because your measurements aren’t exactly the same as the pattern doesn’t mean you necessarily need an adjustment unless you see fit issues. I would recommend making adjustments from the start if you have a significantly different cup size than the pattern is drafted for.
First, we need to mark in the seam allowance along your dart and armscye. French darts are different to standard bust darts as they are cut out of the pattern before being sewn, and as such include seam allowance. The reason for this is that the dart legs are curved and would not be easily sewn with the dart intake intact, and in more angular French darts can be quite a significant amount of fabric which creates unnecessary bulk.
Dove’s French dart has a seam allowance of a ¼” (0.6cm), which tapers along the cut line to the dart point. The armscye has a seam allowance of 5/8” (1.5cm).
We then need to trim the seam allowance from the dart (only the dart) so we have a nice clean slate to make changes to. Once that’s done, we can draw in our slash lines!
Our first line is going to help us find the pattern’s bust apex, which sits at the most prominent point of your bust. Darts exist to help the fabric conform to your body and dart points (the end of the dart) are drafted to be slightly offset from the bust apex to make a smooth transition and to prevent you having a really pointy look to your bust! The larger the bust the further away from the bust apex the dart point will need to be.
Dove is drafted with the apex ½” (1.2cm) beyond the dart point, but this can vary between patterns so always check on the pattern you are working on. A general rule of thumb for most patterns is to try 1” (2.5cm) from the dart point. Another way to find the bust apex is to hold the pattern up to your body or dress form to help find it.
Your own bust apex might be more or less than ½” (1.2cm) from the Dove dart point, but for the purpose of this tutorial we will use the ½” (1.2cm) that Dove has been drafted with. Ok, rulers and pencils at the ready!
LINE 1: Draw this first line through the centre of your dart, through the dart point, and ½” (1.2cm) in towards the centre of your blouse (this line will be a continuation of the dart’s cut line, so you may choose to draw this in before you remove the dart seam allowance). Mark your bust apex at the end of this line.
(Note: because French darts are curved your ruler isn’t going to be sitting nicely in the centre of the open end of the dart when you draw LINE 1, but that’s ok, just focus on being centred in the end section of the dart)
LINE 2: Next, draw a line from the bust apex you just marked, up to your armscye, about 1/3 of the way along the armscye. On Dove, you can use the first sleeve notch.
LINE 3: Draw a line down from your bust apex, all the way to the hem. This line should be parallel to the grain line & centre front of your bodice.
LINE 4: Finally, draw a line perpendicular to the grainline, between LINE 3 and the bodice centre front. It doesn’t actually matter exactly where this is, but about ½ way down LINE 3 is good place.
Now we are going to slash along these lines. Take a deep breath, make a cup of tea if you need it – you can do this!
Cut LINE 3 from the bottom of the pattern to the bust apex, then along LINE 2 up to the armscye, but stop just before the stitch line we drew earlier! (just over 5/8” or 1.5cm from the edge of the armscye).
We are going to cut the rest of LINE 2 from the other side. Make the small snip from the pattern edge to the stitch line, but again stop just before the line. This little bit that we have left is going to act as a hinge, so don’t cut all the way through. The reason we are using the stitch line as our pivot point (instead of the pattern edge) is so the armscye will stay the same size, and our sleeve will still fit perfectly and won’t require adjustments.
Next cut LINE 1 from the dart point to the bust apex. Do not cut completely through the pattern paper at the bust apex. 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.
I’ll start with Full Bust adjustments as these are more common.
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 (i.e. keep the distance the same all the way down). For this example I’ve used an adjustment of 1″ (2.5cm) which will add a total of 2” (5cm) to our pattern.
With our hinges keeping the sections attached, you’ll notice that the slashed pattern is being moved down and to the side. The bottom of the armscye has been pivoted upward, and the section under the dart has been shifted down, opening up LINE 1, and making our dart wider! Place paper underneath your pattern and tape above line 4 to secure these changes.
Now you need to fix the hemline, as you’ll notice the centre front is now slightly shorter than the rest of the hem. Cut along LINE 4, all the way through, then move it down till it is in line with the new hemline. I like to use my ruler to keep it straight. You can now tape LINE 4 and the rest of LINE 3 to secure the placement.
Now we need to draw in our new dart point and finalise our other changes. You have two choices now. You can either mark the dart point back in based on the pattern draft if you think that’s about right for you, or you may choose a new dart point based on what works for your body. This is why we love sewing, you get to choose! An easy way to figure out the best spot is to hold your altered pattern up to your body and see if the drafted apex is right for you. If your apex is in significantly different a position, mark it, and then make sure that your dart is pointing towards this apex point.
For the purpose of this tutorial we’ll use the drafted amount so our new dart point will still be ½” (1.2cm) back from out bust apex (which is now our bust apex hinge), so it will basically be centred between the markings of our old dart point. We then need to redraw our stitch lines to now taper gently from the side seam ends of the dart legs, to this new point. Once we know where we need to stitch, we can then add our seam allowances back in, measuring ¼” (0.6cm) in along these new lines. There will be a point (when the stitch lines are ½” or 1.2cm apart) where the two seam allowances meet. If this point is more than just over ¼” (0.75cm) away from the dart point, then you will need to add in a cut line like the original pattern. However, if your adjustment is larger, your dart will be steep enough to remove the necessity for the cutline completely.
To make sure you have the correct angle for the side seam edges of your dart seam allowance, when you are cutting away your excess paper, first cut out just the triangle of paper between the inside edges of your dart. Then carefully bring the seam allowances together as if you were making the dart, and fold the seam allowances down towards the waistline like you would after you sewed your dart. Holding this in place, cut away the excess paper along the outside edge of the pattern piece which is now a continuous line. You will cut the seam allowances underneath, and they will now be the right shape so that they sit flush with the rest of the side seam when sewn.
Once we have finalised our new & improved dart, we can wrap up the rest of our changes. Draw in the rest of the hem and centre front seam allowance in the openings made by LINE 3 and LINE 4, and smooth out the armscye seam allowance if LINE 2 made any disruptions to its curve. You may choose to add a bit more tape to completely secure everything now. Then grab those scissors back out and cut away any excess paper we don’t need. Just one extra adjustment left to do now, and we’ll be done!
Dove includes a hem facing piece for a beautiful finish, so we need to adjust our facing to fit our new hem width. This one’s an easy one, just line up the facing at the side seam and mark where LINE 3 runs through the facing. Cut through your facing’s LINE 3, then spread and shift down to be in line with your centre front hem (note: the facing centre front should be aligned with the stitch line, not the edge of the pattern piece which includes seam allowance for the centre front seam). Add a scrap of paper underneath to fill in the gap and tape down, then you just need to draw in the new facing edges, cut away any excess paper, and you’re done! Woo!
Now lets chat about Small bust adjustments.
For a SBA, you’ll be using the same slash lines, but you will be overlapping instead of spreading.
Measure from LINE 3 towards the centre front the amount you will be adjusting, and mark. For this example I making a SBA of ¼” (0.6cm) which will add a total of ½” (1.2cm) to the front bodice. Now overlap your pieces of LINE 3, keeping them parallel to the grain line, and using your markings as a guide for how much to overlap. As you can see, this will also cause your dart to overlap and therefore become smaller. Once you are happy with the new positioning, you can tape LINE 1 & 2 and down LINE 3, stopping before LINE 4.
Like with the FBA, the centre front hem is no longer in line with the rest of the hemline, but in the SBA, it is now slightly too long. Cut along LINE 4, and shift the piece upwards so that the hem is again aligned. Make sure your LINE 4 overlap is even all the way across, and your centre front edge is still nice and straight. Tape in place.
We now need to draw in our new dart point. It should still be ½” (1.2cm) back from the bust apex (which is now our bust apex hinge), and will be centred between the markings of the old dart point. The stitch line will need to be adjusted slightly to taper nicely to this new point, after which we can add our seam allowance back in. Pop a piece of paper underneath your dart & lower armscye and tape down along the dart legs so you can draw in the ¼” (0.6cm) seam allowance along the new dart legs. There will a point (when the stitch lines are ½” or 1.2cm apart), where the seam allowances meet. Lining up your ruler with this point and the new dart point, you need to draw your cut line, stopping around ¼” (0.75cm) before the dart point.
To make sure you have the correct angle for the side seam edges of your dart seam allowance, when you are cutting away your excess paper, first cut out just the triangle of paper between the inside edges of your dart. Then carefully bring the seam allowances together as if you were making the dart, and fold the seam allowances down towards the waistline like you would after you sewed your dart. Holding this in place, cut away the excess paper along the outside edge of the pattern piece which is now a continuous line. You will cut the seam allowances underneath, and they will now be the right shape so that they sit flush with the rest of the side seam when sewn. If needed, you should now also tape and smooth out your armscye which may have been pivoted open by LINE 2, before cutting away any excess paper. And then we’re almost done!
Again as Dove includes a lovely hem facing we need to adjust our facing to fit our new hem width. This one’s an easy one, just line up the facing at the side seam and mark where LINE 3 runs through the facing. Cut through your facing along this line, then overlap and shift the centre front piece slightly up to be in line with the rest of the hem (note: the facing centre front should be aligned with the stitch line, not the edge of the pattern piece which includes seam allowance for the centre front seam). Tape in place, and you’re done! Woo!
See! It wasn’t all that hard after all!
Now one last note! In this tutorial I didn’t want to complicate things, so I have shown the standard method for an FBA and SBA. This standard approach will always result in making the hemline wider in addition to the bust. In another blouse, that might just mean that you would need to remove some width from the side seams of the hem to maintain your correct hip size. However, to maintain the shape of Dove’s statement curved hem, another method may be needed to avoid adding width to your hem, and this also happens to be my personal method for FBAs & SBAs. Instead of maintaining the entire bust adjustment for the full length of bodice, i keep the bottom edge of LINE 3 hinged, to maintain the hemline, and only spread or overlap the whole adjustment amount at the bust apex. There will still be a slight adjustment to the facing, but you will essentially keep the same hip size & hem shape.
If you have any questions let me know in the comments!