16 September 2019

How to Do Bust Adjustments for a Bust Darted Bodice

Bust adjustments bust darted bodice bodice pattern fitting - Tilly and the Buttons

Do you ever wish your me-mades fit better across the bust? Do you find that excess fabric seems to pool around your bust, or that it's too tight? Ever think that the bust darts point in the wrong place on your garments? If you're finding yourself nodding enthusiastically in agreement to any of these statements, then you probably need to do a bust adjustment to your bodice pattern pieces.

It's Nikki here, Product Manager and fitting geek at Tilly and the Buttons, and I'm going to to talk you through how to do a full bust adjustment, a small bust adjustment and how to move the dart on a bust darted bodice.

Now, before we go any further I'd like to give you a little positive pattern pep talk. There are a few diagrams in this post, but whilst they might look quite daunting, they are relatively simple if you follow them step by step :)

How do I know if I need a bust adjustment?

There's a technical and a not-so-technical answer here! The answer depends on your own unique shape and the fit of the garment - you may not need to do a bust adjustment to a loose top or dress, but might have to do one on something more fitted. If you find that things are generally either too tight or too loose in the bust area, then I'd recommend making a quick toile of the bodice, or wearable toile of the whole garment to test the fit around the bust and take it from there. I'm going to briefly cover how you would work out how much to add or subtract from your bust in the adjustment, but do remember this is just a rough framework, and you might not need to do it at all.

Measure your high bust (your upper chest, just under your armpits) and add 5cm (2in). Choose the pattern size with that bust measurement – this is the size you’ll do your bust adjustment on.

Now measure your full bust (fullest part, around the nipples) and compare it to the bust measurement on the pattern size you just selected.

If your full bust is 5cm (2in) smaller than the pattern, you’ll be subtracting 5cm (2in) from the pattern; if it’s 7.5cm (3in) bigger, you’ll be adding 7.5cm (3in) and so on. If you need to make the bust bigger, you'll need to do a full bust adjustment (FBA) and if you need to make it smaller, you'll need to do a small bust adjustment (SBA).

Since the front bodice pattern represents one half of the top, as the fabric is cut on the fold - or one boob - you'll be adding or subtracting half of that difference. So, if you want to do a 5cm (2in) full bust adjustment, you'll need to add 2.5cm (1in) to the pattern piece.

There are a few ways in which you can do a bust adjustment, but the method I'm going to show you today is the "slash and spread" method. It sounds a bit aggressive but this just means that you do the adjustment by cutting into your pattern piece and either spread it apart to create more space at the bust, or overlap it to make it smaller.

To do a bust adjustment you will need:
  • a ruler (or pattern master if you have one)
  • glue stick and/or sticky tape
  • pencil
  • paper scissors
  • extra paper

As you'll be merrily snipping into your pattern piece with wild abandon for these adjustments, I thoroughly suggest tracing off the front bodice pattern piece so you can keep the original one intact in case you need to make any further adjustments. Make sure you trace all the notches, the dart and 'lengthen or shorten here' lines onto the new pattern piece.

Got your scissors and ruler at the ready? Ok, let's go. And remember, you've got this!

Full bust and small bust adjustments



The first few steps of both the full bust adjustment and small bust adjustments are the same. Once you finish the steps in this section, pick either the full bust or small bust adjustment sections below :)

Before we grab our scissors and start snipping into our pattern, we need to draw on the front bodice pattern piece in several places. I've drawn these in different colours to make them easily identifiable.
Firstly, we need to find the approximate bust apex, otherwise known as the bust point. The bust apex will differ from person to person, as all of our bodies are different. The easiest way to find this is to hold the pattern piece up to your body. Hold the front bodice so the shoulder line lies 15mm (5/8in) over your actual shoulder line. Make a marking where the fullest part of your bust is (the fullest part of the bust, most likely the nipple). This is your apex. 

Now, if you draw a straight line through the centre of the dart, the apex should sit around 2.5cm (1in) away from the point of the dart, and this is where it's sitting in the diagrams below. If your bust apex isn't this distance from the tip of the dart or isn't in line with it, you can easily move the dart. Please see the "moving the bust dart" section below. 

Bust adjustments bust darted bodice bodice pattern fitting - Tilly and the Buttons

Draw a line through the centre of the dart from the side seam to the tip, and to the apex. This is the green line on the above diagram. The end of this line is also the bust apex. 

Next, draw a straight line from the bottom of the bodice up to the bust apex (the end of the green line) and then pivot to hit around a third way up the armhole (technically, the armscye). I've shown this line in purple here. Make sure the vertical line is parallel to the grainline. Where the line joins the armhole, mark the seam allowance - this is shown here with a dotted line.

Finally, draw a horizontal line at the bottom of the pattern, on the opposite side of the vertical line to the dart. This is shown here in pink. It doesn't have to be anywhere specific, just as long as it's nearish the bottom is fine. 


Bust adjustments bust darted bodice bodice pattern fitting - Tilly and the Buttons

It's time to grab those paper scissors and get snipping! We need to create two "hinges" on the pattern which will allow us to move the paper without it separating. This is achieved by stopping cutting a smidge before the end of the line - don't be shy about getting right up to the line, but try as hard as you can to not actually snip through!

The first line to cut is the green line through the dart. Cut, starting at the side seam and stop just before the end. Now, cut through the purple line, starting at the bottom of the bodice and ending a smidge before the dotted seam allowance line. From the other side of the seam allowance, cut from the edge at the armhole and stop just before the seam allowance line.

You will now have two pivot points - one at the tip of the dart and one at the armhole. They are very delicate so be careful! The final line we need to cut is the pink, horizontal line. We don't need to create a pivot point so cut right across the line to separate it from the rest of the pattern piece.

Full bust adjustment (FBA)

Bust adjustments bust darted bodice bodice pattern fitting - Tilly and the Buttons

Get a piece of paper around the size of your bodice pattern piece and draw two vertical lines, with the distance between them the amount you want to increase the bust size by, divided by two. So for example, if you want to add 5cm (2in), the distance between the lines will be 2.5cm (1in). Don't forget, the front bodice piece represents one half of the top (or put more simply, one boob), so a 2.5cm FBA will add up to 5cm (2in) overall.

Carefully place the pattern piece on top of the paper. We need to line up the vertical, cut lines on the pattern with these lines, using those very helpful pivot points we've just made. The easiest way to do this is to align the vertical line above the pink line first. Stick it down using a glue stick or sticky tape. Now, gently pull the dart down so the vertical edge under the dart sits flush with the other vertical line and stick in place.

This will have increased the size of the dart and therefore made the pattern piece longer than it was originally, so we need to extend the bodice on the other side. Draw a vertical line down from the straight seam, and a horizontal line at the bottom. Using these lines as a guide, align the remaining bodice piece (the one we made when we cut the pink line) and stick in place.


Bust adjustments bust darted bodice bodice pattern fitting - Tilly and the Buttons

Next up, we need to re-draw the side seams and the dart (aka the sticky out bit) so the seams match up. 

To re-draw the dart, measure 2.5cm (1in) horizontally from the bust apex towards the side seam. This will be the new dart point. Draw new dart legs, starting at their original positions at the side seam to meet the new dart point.

You'll notice that the armhole (armscye) looks a bit uneven. Draw a new line to smooth out this seam. 

Bust adjustments bust darted bodice bodice pattern fitting - Tilly and the Buttons

We now need to re-draw the side seams at the dart. Now, there's a cheat way and a "proper" way here. The cheat way is to extend the current side seams so that they meet in the middle to make a new dart. This isn't always 100% accurate, so if you want to know how to do the proper way, read on :)

Fold the bottom leg of the dart up so it meets the top dart leg. This is a bit tricky to do on paper and will make your pattern piece stick out. The most important bit here is making sure the dart legs meet up on the side seam. Temporarily tape the dart together so it doesn't slip out of place. Roll a tracing wheel over the side seam - if you don't have a tracing wheel, punch through the paper every 5mm (1/4in) or so to mark it. 

Bust adjustments bust darted bodice bodice pattern fitting - Tilly and the Buttons

We're on to the last step! Un-tape the dart and draw over the markings you made with the tracing wheel or pins. The final thing we need to do is bring in the side seam so it's not too big at the waist. At the bottom of the bodice at the side seam, measure in the amount you increased the bust by - i.e. 2.5cm (1in) if that's what you added - and redraw the side seam with a smooth, curved line. This is shown above in blue.

All that's left to do is cut away any excess paper to leave you with a newly altered bodice :)

And that's it, you've successfully done a full bust adjustment on a bust darted bodice! Give yourself a huge pat on the back, you've just gone up a sewing level (+100 sewing points).

Small bust adjustment (SBA)



Bust adjustments bust darted bodice bodice pattern fitting - Tilly and the Buttons

We need to work out how much we want to decrease the bust by. If you want to decrease the bust by 5cm (2in), we need to decrease the pattern piece by half that amount, as this adjustment will be applied to both sides. 

Measure the amount you want to decrease the bust by from the bust apex away from the dart and mark it. Draw a vertical line from the bottom of the bodice up to the marking you just made, and a bit beyond. This line should be parallel to the grainline. 

Gently hold the bottom of the pattern piece, under the dart, and manoeuvre it so the cut line is aligned with the vertical line we just drew. This with move the dart slightly up. Stick in place with a glue stick or sticky tape.


Bust adjustments bust darted bodice bodice pattern fitting - Tilly and the Buttons

The bodice will not be slightly shorter than it was originally. We now need to re-attach the little rectangular bit of bodice we cut earlier. This is super easy to do - line it up with the rest of the bodice at the vertical side seam and the bottom and stick in place. 

Bust adjustments bust darted bodice bodice pattern fitting - Tilly and the Buttons

All that's left to do is to re-draw the seams. Get a piece of paper and stick it underneath the bodice - we only need to redraw the side seam and smooth out the armhole a little so it only needs to cover those areas. 

The seam at the armhole (the armscye) will be a bit wonky after all that pivoting, so smooth out the seam with a pen or pencil. We also need to re-draw the dart. Horizontally measure 2.5cm (1in) away from the bust apex towards the dart - the bit where all the lines are meeting - and mark it. This is the new dart point. Draw from this new point to the end of the dart legs. They might be hidden underneath the paper as there will be some overlapping here, so if you can't see it clearly fold back the top layer to reveal the ends of the dart legs.

Lastly but by no means least we need to bring out the side seam under the dart. As we have reduced the width across the bodice we need to add it at the sides so that it's the correct width at the waist and not too small! Say for example we reduced the bust by 2.5cm (1in), measure out by that amount at the side and draw a smooth, curved line to meet the side seam just under the dart.

And hey presto, you have successfully done a small bust adjustment on a darted bodice. Happy days indeed.  

Moving the bust dart

The final bust adjustment we're going to cover is moving the bust dart. All of our bodies are different and you may notice that the dart is sitting too high or low for your bust, and perhaps too far in or out. If it's sitting in the wrong place, the fullness will be hitting your bust at the wrong position and it can make the dart look a bit pointy too.

The bust dart is meant to point towards your bust apex (the fullest part of the bust, usually the nipples). The easiest and quickest way to find out if the dart is in the right place on the pattern is to hold the front bodice so the shoulder line lies 15mm (5/8in) over your actual shoulder line. Make a marking where the fullest part of your bust is (the fullest part of the bust, most likely the nipple). This is your apex. Alternatively, you can also make a quick toile of the bodice and mark on the fabric where the apex is, and compare it to the pattern piece.

If you draw a line down the centre of the dart, the bust apex should sit approx 2.5cm (1in) beyond the tip of the dart. If your marking is in a different place, you may want to move the bust dart.

If you think this applies to you and that you need to move the bust dart to a new position, then read on.

Moving the bust dart vertically

Bust adjustments bust darted bodice bodice pattern fitting - Tilly and the Buttons

First things first, we need to draw a rectangle around the bust dart and cut it out to completely remove it from the bodice. Make sure the vertical line is parallel to the grainline.

Bust adjustments bust darted bodice bodice pattern fitting - Tilly and the Buttons

Whilst keeping the vertical lines flush with each other, move the rectangle up or down by the amount you want to move the dart by. Stick down using a glue stick or sticky tape. Re-draw the side seams so that they join up smoothly with the dart legs. And that's it, easy peasy :) 

Moving the bust dart horizontally and vertically

Bust adjustments bust darted bodice bodice pattern fitting - Tilly and the Buttons


Depending on where your bust apex sits, you might want to move the bust dart horizontally and vertically. Luckily, this is pretty simple to do! 

Start by drawing a rectangle around the dart and cut it out.

Bust adjustments bust darted bodice bodice pattern fitting - Tilly and the Buttons

Draw a vertical line down the middle of the rectangle and cut it to split it in two.

Bust adjustments bust darted bodice bodice pattern fitting - Tilly and the Buttons

Work out how much you want to move the bust dart by. In the above example I've moved it 1.5cm (5/8in) down and 1cm (3/8in) out to the side seams. Make sure you keep the rectangle parallel to the existing horizontal and vertical lines. Take the piece with the tip of the bust dart and stick it down using a glue stick or sticky tape to its new position. 

Bust adjustments bust darted bodice bodice pattern fitting - Tilly and the Buttons

Take the remaining piece of the rectangle and line it up with the side seams as best you can, and the first bit of paper you suck down. If you're moving the dart tip towards the side seam, there will be some overlap (like the example above). Stick it in place. Redraw the side seams. You'll also need to re-draw the dart - draw from the point of the dart to the end of the dart line at the side seams.

If you want to move the dart inwards, the process is exactly the same, except you'll need to add a bit of paper underneath as there will be a gap here instead of an overlap. 

And that's it! I hope you found this post useful. Don't forget, you can use these adjustments on any pattern with a bust darted bodice so make sure you bookmark this page so you can revisit it again.