MN2107 Olive / Pattern Alterations & Adjustments / Sewalongs / Tips & Tutorials

How to do a Full Bust Adjustment on a Dartless Pattern

Megan Nielsen Patterns | How To Do A Full Bust Adjustment On A Dartless Pattern

Knowing where to begin with a bust adjustment on a dartless pattern like Olive can be a little confusing, but not to worry, we’ve got you covered! Today’s very thorough tutorial is brought to you by Naomi our wonderful Design Assistant at Megan Nielsen Patterns, and we really hope you enjoy it! Take it away Naomi…

We’re going to go over two different methods in this tutorial, one which will accommodate for a full bust by adding a dart, and one which will give more room for a larger bust by pivoting the increase into the hem and keeping the top dartless. Both are really easy, but will produce two different final looks! Regardless of which you decide to use, they both start the same way, but before we get to that, let’s talk about what a bust adjustment actually is, and whether you even need one!


Most sewing patterns, including our 0-20 range are drafted on a B cup block and most Curve patterns like our 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. Because of the dartless nature of Olive, we’ve found that SBAs are very rarely necessary, so we haven’t included it in this tutorial. Another reason why is that the shape of the drop shoulder armhole in this pattern means a traditional bust adjustment which hinges at the armscye, is quite limited in how much can actually be pivoted out, so what we are covering today isn’t going to be very useful!


So how do you figure out if you need a bust adjustment? There are a couple of ways to find out!


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.


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.


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


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 Olive). We’ll call this your equivalent bust for purpose of explanation. Choose your pattern size based on this “equivalent bust” measurement. Your full bust measurement less the calculated equivalent bust measurement is the amount of your FBA.

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.

Megan Nielsen Patterns | How To Do A Full Bust Adjustment On A Dartless Pattern | Mark Seam Allowances & Draw Slash Lines

Now that we know how much we want to adjust the bust by, we need to get our pattern ready. This includes marking the stitch line of the armscye, 5/8” or 1.5cm in along the edge of the pattern, as well as marking our bust apex- except, bonus! We’ve actually included Olive’s bust apex in the pattern to help in this exact situation, woo! The bust apex I’m talking about is the point in the pattern which sits at the most prominent point of your bust. The marking on Olive is an “average” that the pattern is drafted on, but it’s worth noting that your bust apex might not be in the same place! We all come in different shapes as well as sizes, so your apex might be higher, lower, or more to one side or the other. One way to find your own bust apex is to hold the pattern up to your body, keeping the centre front and side seams in the correct position, and to see where the fullest part of your bust sits in relation to the pattern (note: it’s important to consider the sort of underwear you intend to wear with your garment when you do this! If you’re going to wear anything with padding or that changes the natural place your bust sits, you need to take that into account). This is also a method you can use on patterns which don’t include the bust apex marking.

Once we have that done, we can start drawing our slash lines. Rulers and pencils at the ready!

LINE 1: This line is drawn from the side seam to the bust apex. The exact point along the side seam that LINE 1 starts is up to you, but just under the curve of the underarm is a good place. This line will determine the position of a dart if you chose to add one.

LINE 2: Next, draw a line from the bust apex, up to your armscye. It should be approximately 1/3 of the away along the armscye.

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.

Megan Nielsen Patterns | How To Do A Full Bust Adjustment On A Dartless Pattern | Cut Slash Lines

Now we are going to slash along these lines. Take a deep breath, clean you glasses, do a star jump if you need to loosen up – 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 (if you are choosing to add sleeves) will still fit perfectly and won’t require adjustments.

Next cut LINE 1 from the side seam 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 in the next step – spreading our pattern at the slash lines!

Megan Nielsen Patterns | How To Do A Full Bust Adjustment On A Dartless Pattern | Spread At Slash Lines

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? (1.25cm) which will add a total of 1” (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 slightly, and the section under LINE 1 has been shifted down, opening up something resembling a dart! Place paper underneath your pattern and tape along LINE 2, the top edge of LINE 1 and the right side of LINE 3 above LINE 4 to secure these changes.

It’s at this point that our two methods deviate, so it’s time to decide whether you would like to keep your new dart, or pivot it into the hem! *dramatic who wants to be a millionaire decision music plays in the background*. Personal preference is the most major factor, but there are a couple of other things to consider too:

Megan Nielsen Patterns | How To Do A Full Bust Adjustment On A Dartless Pattern | Option One: Adding A Dart
  • Darts are great – they mean that you will be able to keep the general shape of the original design, without changing the shape of the hem dramatically, but they also mean there will be a section of your top’s surface which is disrupted. If your fabric has stripes or a pattern, the dart is going to change their direction and cut out a section which you may not want. On the other hand, pivoting the dart into the hem ends up increasing the angle of the side seam for the front of the top, which may make pattern matching your front & back at the side seam more difficult.
Megan Nielsen Patterns | How To Do A Full Bust Adjustment On A Dartless Pattern | Option Two: Pivoting Out The Dart
  • Pivoting is also great – it’s easy, and means you don’t have to sew a dart, but it does mean a bigger overall change to the look of your top, and it’s more important to consider the fabric you are using when pivoting. The pivot increases the hem volume to accommodate for your fuller bust, and if your fabric doesn’t have enough drape, this extra volume may simply stick out and can end up looking boxy. If your fabric is more structured, and that’s not the look you’re hoping for, a dart might be for you!

Ok, times up! Have you made your decision?

Megan Nielsen Patterns | How To Do A Full Bust Adjustment On A Dartless Pattern | Option One: How To Add The Dart
Megan Nielsen Patterns | How To Do A Full Bust Adjustment On A Dartless Pattern | Option One: How To Add The Dart

So you’ve decided to add darts, great! First thing we need to do, is 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.

Next is to draw in the legs of our new dart. To do this, we will also need to mark the new dart point (i.e. the end point of the dart), which is actually different to the bust apex. Darts exist to help the fabric conform to your body and dart points 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. As a general rule of thumb though, 1” (2.5cm) back from the bust apex towards the side seam, is a good place to put your dart point. Mark this point, centring it in the space between each side of LINE 1, and from there, use your ruler to draw two lines out to the side seam edge of the pattern, connecting the corners of your dart opening to your dart point. These dart legs will be the stitching lines of your new dart.

With that complete, we just have some final touches to do and we’ll be done! You can draw in new edges for the hem and centre front, which were broken up by the shifting of LINE 3 & 4, and trim away any excess paper. The shape of the armscye may have been disrupted by the new angle of LINE 2, which can simply be smoothed and trimmed also. For the new edge of your dart opening, you need to create a shape that when sewn together and pressed downward, it sits perfectly in line with the side seam. The best way to do this, is to simply fold the pattern as if you were actually making your dart, bringing the dart legs together and folding the paper between them in half. With these lines matched, and the folded paper beneath being held downward towards the hem, simply trim along the edge of the pattern, which should look almost like the original continuous edge we started with before LINE 1 was cut & spread. Once you have cut through all the layers of paper, you can then unfold the dart. You should now have a shape that will sit flush with the rest of the side seam when sewn.

And that’s it, you’re done! Woo!

Now let’s chat about our second method.

Megan Nielsen Patterns | How To Do A Full Bust Adjustment On A Dartless Pattern | Option Two: How To Pivot Out The Dart
Megan Nielsen Patterns | How To Do A Full Bust Adjustment On A Dartless Pattern | Option Two: How To Pivot Out The Dart

So you’ve decided to pivot out the increase, awesome! This method involves moving some of the additional volume we added to accommodate a fuller bust, from the dart position, into the hem of the garment. To do this, all we need to do is to pivot the section of our pattern below LINE 1 and to the left of LINE 3, upward towards the other edge of LINE 1. Once these lines are matched back up, the space that used to be between them, has now been transferred to the opening of LINE 3.

We can then secure all of LINE 1 & 3, before moving on to marking and cutting our new hem. Cut along LINE 4, all the way through, then move it down till it is in line with the new hemline. The position of this new hemline is up to you and your own preferences! It’s best to add a little length, as hemlines can appear shorter when fabric needs to sit over a fuller bust, but you may not want it too long. It’s for you to decide! Just remember that it’s easier to trim off length later than to add it because it’s too short. I have chosen to make my new hem somewhere between the two bottom corners of the angled section.

Once you have drawn your new hem, and secured the edges of LINE 4, fill in the gap you just created by spreading LINE 4 and smooth out any disturbances to the curve of the armscye caused by the new angle of LINE 2. Then all you need to do is trim away your excess paper, and you’re done! Great work!

How did you go? Wasn’t that hard after all, right?

Before we finish up though, I’ve got a couple of extra notes for you!

Darts +  Breast Pockets

To keep my diagrams nice and clear, I’ve left out the breast pocket that you can chose to add in Olive, but that doesn’t mean that you have to as well! When you cut out & transfer the necessary markings from your bodice front pattern piece onto your fabric, just mark the top and bottom corners of the pocket edge closest to the centre front. They shouldn’t have been disturbed by any of our alterations and will make sure your pockets go on nice and straight. After you have sewn your dart, it’s really important to make sure to press it well, so that the right side of the dart is nice and open. It’s best to press darts using an ironing ham, which mimics the shape of your bust and prevents the dart from getting squished flat. With the ironing ham still underneath and right side up, place your prepped pocket on your top, using the two corner markings to line up the first side of your pocket. With the top in it’s curved position over the ham, the pocket should sit nicely and pinning the remaining sides should be quite easy. Once pinned, you can sew around the edges as you normally would! Doing it this way, instead of pinning it with the top flat, means that you’re a lot less likely to get the pocket or shirt under the pocket bubbling and sitting unevenly.

View B Dress & Pivoting

Something else I glossed over, in order to keep this tutorial from slipping into novel-length territory, is that the Olive pattern also includes a dress version! Like we talked about earlier, the dart method in this tutorial is going to keep the hem (or in the case of the dress, the waist seam cutline) relatively the same shape and size, so it isn’t going to interfere with the joining of our gathered skirt to the bodice too much. At the very most, the gathers may be spread slightly thinner over the front because of the slight increase to the front width. The pivoting method on the other hand, is increasing the hem width significantly. In order to keep a nice amount of gathers in your skirt, you would need to increase the width of your skirt front a significant amount too (x2 is a pretty standard gathering ratio, so whatever your waist seam width increased by, you would need to add double that to the width of the skirt front). This might end up meaning you’ll require a seam in your skirt front if your fabric isn’t wide enough and it’s going to be pushing your dress into some pretty wibbly wobbly, major volume territory! Who knows, that might be your flavour! But if it’s not, it might be worth giving the dart a crack instead.

An alternative Dart Method

Megan Nielsen Patterns | How To Do A Full Bust Adjustment On A Dartless Pattern | FBA Alternative Method

The methods I’ve talked about today are the standard approach to FBAs which will always result in making the hemline wider in addition to the bust. For the those pivoting, it’s unavoidable, but for those who chose to add the dart, this is something that be remedied if it’s not what you want. A straightforward way to fix it, is to simply trim the increase from the side seams of the hips, or alternatively, you can prevent the increase all together! This can be done by leaving the bottom edge of LINE 3 hinged and only spreading the entire bust adjustment amount at the bust apex. The increase at the apex will taper to nothing at the hem and the original hem width will be maintained. Easy as!

If you have any questions let me know in the comments!

About Author

Naomi is the Design Assistant here at Megan Nielsen Patterns, and our resident helping hand. She stays busy assisting Meg with pattern development leg work, getting super excited about good instructional diagrams and making green coloured fabric suggestions for every sample we make. She’s a problem solver, a fabric addict, a serial tea-forgetter and a passionate maker.

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3 years ago

Great detailed tutorial on this adjustment! Thanks for providing this.

Sandra Garnett
Sandra Garnett
1 year ago

Hi Naomi – my shoulder measurement is 38cms with a HB of 97 and a FB of 108, my W is 97. Is the shoulder measurement important when calculating a FBA? Regards, Sandra

10 months ago
Reply to  Sandra Garnett

Hi Sandra,

This is a great question! The shoulder width and high bust are related. The high bust is the most important measurement used, and when you use your high bust method to choose your size then you will find that the shoulder width will be narrower which is usually what women who require an FBA need. I would recommend doing the FBA first as shown, and then if you find that the shoulder width isn’t appropriate adjust after that.
Happy sewing!