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Making a Bust Adjustment to a Pattern

Making a bust adjustment

This guide to making a bust adjustment is the third in a series of technique guides written by Nicola Chadwick – a former senior fashion lecturer. Her business is aimed at providing designers, adventurous dressmakers and pattern cutters with the tools they need to create their own patterns from their own designs. You can find out lots more at

Nicola also has a website Wabi-Sabi Studio – where you can create 7 dolls with their own wardrobes.

Did you know that most commercial pattern companies make their patterns to fit a B cup size? If your cup size is larger or small than this then you begin to realise that the garments you are making from these patterns will never fit you perfectly.

This leaves the full busted lady, and there are many, with no choice but to select a pattern size to fit her bust size. This results in a garment that fits poorly everywhere else. The smaller busted lady is also faced with the same problem but in reverse. 

I encounter this problem myself as I am an F cup and have a very small skeletal frame. As a pattern cutter and pattern grader I am acutely aware of how the changes I make to a pattern in one area impact the fit of the garment in other areas. In certain areas a change of a millimetre can have an impact. In other areas centimetres are required. If you simply add on extra (or subtract) all around the pattern you are creating even more fitting problems!

If you google FBA (Full Bust Adjustment) or SBA (Small Bust Adjustment) you can find many articles and blog posts on the subject. As with any information you discover on the internet there are some good articles out there and some shockingly bad ones! Some of the methods suggested will lead to more fit problems than you started with.

If you are an AA or A cup, then you may get away without making any pattern adjustments. It also depends on the style of the garment and your fit preferences. If you are a C or perhaps a D cup, then you may also be fine.

How do I know if I need to make a Bust Adjustment on my pattern?

Do your blouses gape or fail to sit properly at the centre front?

Is there a bump or folds of fabric above the fullness of your bust?

Do the shoulders of your garments never sit correctly?

Does the fullness of the bust shaping or the location of the darts not match your own bust shape?

Does the front hem of your garment not sit level with the rest of the hem line?

Do the darts of the garments you are sewing fail to ‘aim’ towards the fullest part of your bust?

If the fit issues mentioned above sound familiar to you then it’s likely that you would benefit from adjusting the bust area of your patterns. Once you have solved these problems you will never look back!

The goal of an FBA or SBA is to adjust the bust without altering the fit in all other areas of your garment. When making changes around the bust area we must also consider where our bust sits. I can certainly say that my bust level (and bust points) are much lower now than they were when I was a student. This is a detailed topic on its own and I have a useful blog post on raising or lowering the bust level of a pattern if you want to delve into this area in more detail.

A guide to bust fit terminology for dressmakers

Raising or lowering the bust level is quite straightforward in theory – knowing how much you need to adjust it is more difficult to work out. This is where making a toile is essential. I covered the importance of making a toile in this article if you would like to know more about that.

You can take an educated guess by placing the pattern piece to your body and marking on where your bust level and bust points are. I know for myself I will always need to lower the bust level on a commercial pattern. You can make an ‘estimated’ adjustment first and make a trial garment, then perfect the fit of the bust level and bust points as required.

You can find much more information on how to find a bust point on any commercial pattern by looking at this post on my blog page.

Let’s look at how to locate the bust point and bust level on a pattern that has no darts, or perhaps one dart. This will help you to understand the bust area and illustrate how to relocate a dart to the new bust level.


You will need the following equipment:

Some pattern cutting paper

A pair of scissors

A sharp pencil (2H is best)

Some sticky tape

The pattern you would like to adapt

A ruler and a tape measure

How to lower the bust on a sewing pattern

1. Take your pattern piece front and place accurately to your body. Make a mark where your bust point lies – remember this is the fullest part of your bust. To do this accurately you must be wearing a good supportive bra.

Your bust point may be higher or lower than the pattern. The technique below can be used as a solution to both.

How to lower the bust on a sewing pattern

 2. If you have no darts on the pattern then simply make a mark to identify your bust point and your bust level. You now have the location marked for the next step of making a Full Bust Adjustment (FBA) or a Small Bust Adjustment (SBA.)

If you have a dart or darts on your pattern, you will need to find the centre of each existing dart. Connect this central point to your own marked bust point – then continue to mark in new dart legs, connecting both legs to the new bust point. This dart will need to be shortened by at least 2.5cm (1 inch) for sewing. If you sew a dart right to the bust point it will look very unsightly!

I am aware that I am using some technical language here – if you are asking yourself, what on earth are dart legs! Here is a little help. If you would like to know a little more about this then you can head over to my blog page for much more information!

What a re dart legs on a sewing pattern

Don’t forget to fold in the dart, as it would sit when it is sewn, this gives you the correct shaping.

You may need to stick some pattern paper to the side of the pattern to allow you to fold the new dart in. Cut the new dart while it is folded. This gives you the correct shape. Blend the side seam to make it smooth again.

You now have the correct bust level and your darts are aiming towards your bust points. This is a great achievement and will vastly improve fit. If you need to make an FBA or SBA you are now ready to go ahead and make the adaptations.

Let’s look at making an FBA (SBA is just the reverse of an FBA) to a pattern that has no dart at all, for example a t-shirt pattern. Larger busts look much better in garments with bust darts, so we will also introduce a dart into this basic pattern shape to perfect the fit.


Pattern Preparation

If your pattern has seam allowance, most commercial patterns have 1.5cm seam allowance, then mark this seam allowance with a pencil inside the pattern piece.


1. Place your pattern to your body and mark the bust point if you haven’t already done so.

How to do a full bust adjustment on a sewing pattern
How to find the bust level on a dressmaking pattern

2. Place your pattern on the table. Drop a perpendicular line from your bust point mark to the hem of your pattern piece.

how to alter sewing patterns

3. Mark a line on your pattern where you would like the extra fullness to form, the shoulder is best for a very full bust that has a lot of volume above the bust points. You can also select a position under the armhole or both if you want to fit a very large bust.

How to adjust a sewing pattern to fit a large chest

 4. Now you need your scissors – slash up the vertical line right up to your marked bust point. Continue up the line you marked for your extra fullness. STOP at the point where the seam allowance starts.

 Keeping the pattern piece slightly attached at the pivot point open the pattern piece up. If the garment is being made with stretch fabric you don’t need to open the pattern up as much as a garment made with woven fabric, half is enough.

How much will you need to open the pattern? This all depends on the shape of your bust and how many cup sizes you want to increase the pattern by. There is a 2cm bust girth difference per cup size so try 1cm (as you have two sides to the garment) as a starting point. You can then adjust again to perfect the fit. The illustration below shows you where you need to measure.

How to increase the bust size on a sewing pattern

5. You will need to introduce some extra length at the centre front. This allows for the extra fabric you need to travel over the larger bust and prevents the front hem from dipping upwards. Cut along the bust level from the CF to the BP and drop the centre front by the quantity you require, try 2cm ( just under 1 inch) per cup increase and adjust as needed.

How do you alter a sewing pattern?

6. Now let’s introduce the new dart. Let’s put a French dart in at a position radiating from the waist level. Plan a dotted line where you would like this new dart to be. Cut up the dotted line, keeping it attached by a couple of millimetres right at the end. Pivot the side panel back to the hemline.

How to make bust adjustments on your sewing patterns

7. Draw in the new dart, connect the opening of the dart mouth to the bust point. Find the centre line of the dart and draw this in. Take the dart apex back at least 2.5cm for a small adjustment. The larger the bust the further away the dart tip needs to be from the bust point. This is also a matter of personal preference.

Essential bust adjustment techniques

 It’s worth noting here that you have only made changes to the pattern where you need them. The hem circumference remains the same as does the side seam length, once the dart is sewn in. There are no changes to the armhole or the shoulder or the neck. This means that the back of your pattern piece is cut as normal.

How to get sewing patterns to fit well around the chest area

I can’t promise that you will achieve the perfect fit on your first attempt. By making small adjustments to the fit using the methods explained you will certainly get there.

This subject area is vast and it’s impossible to cover all aspect of bust adjustment here. If you would like more information, for example how to make a SBA ( the exact opposite of the steps we took above) then continue reading at my blog page I am also happy to answer any questions you may have. Keep a look out on my YouTube channel for useful pattern adaptation videos too

Why not read Nicola’s guide to adjusting a neckline on a sewing pattern next?