A full bust adjustment to a sewing pattern is simple and easy to do when you require extra room without adding space at the shoulders and armhole.  It is without a doubt the most requested tutorial I have ever gotten.

full bust adjustment

To be honest with you, I could write a whole book about this, but there are some very good ones out there that are already.  Unfortunately, none of them will answer all your questions.  The reason is that altering a pattern for a better fit depends on your measurements and the style of the pattern.

I will not go into more details, the argument can last many weeks, so it makes the perfect topic for another article.

Before we get started, I think it is important to mention that this is an intermediate to advanced sewing technique.  It’s probably not something you want to try on your first garment project. But if you’re already comfortable with garment sewing and want to move your sewing skills up to the next level where you can really start to customize patterns to fit perfectly, please read on!

full bust adjustment

Getting started

There are generally considered to be three types of pattern alteration which are listed below:

Pivot & Slide Method Slash & Slide Method Seam Method
Where we take a pin and move the pattern as a pendulum to increase or decrease it in size without changing the armhole size, normally used when more than one alteration needs to be done, for example, enlarge the bust, waist, and hips without making the shoulder wider. Where we use darts and specific measurement point to cut the pattern to change it to your measurements.  Use only if you are increasing the size up to two inches.  This is not the first time I talk about this, I have mentioned this rule on the walking shorts sew-along.  It is possible to alter the pattern further than inches but be aware that a bigger amount will result in an increment of the armhole and a change in the shoulder slope. This is also known as the Advanced Method made on muslin where multiple alterations are necessary.

I’m going to be using our recent pattern and tutorial featuring the Proteus Cardigan Pattern for Many Occasions to demonstrate this technique.  It will form part of the sew-along we’re going using this pattern.  However, you can use this technique on other patterns as well.

cardigan pattern
So-Sew-Easy.com

Materials for making a full bust adjustment:

  • pattern making paper
  • ruler
  • grading ruler
  • 2B pencil
  • tape measure
  • sticky tape
  • pin or awl

How to make a full bust adjustment

I will show you how to make a full bust adjustment by the Slash and Slide Method, and a combination of the Pivot and Slide Method.   I will not be showing you how to use the Seam Method because that is better demonstrated on a video with a life model.  We’ll cover that one at a later time.

full bust adjustment

Step One:  Measure yourself

Use the drawing below to write your measurements.  This FREE template for a full bust alteration can be downloaded from our sister site Sew4Free.  Please remember to join the mailing list while you’re over there to get a new list of FREE sewing patterns every Saturday.  That’s all we ask!

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Download the Free Template

You can download this Handy Measurement Template from our sister site at Sewing4free.com.

All we ask is that you join our FREE mailing list if you would like to get this template.

For help downloading and printing PDF patterns, please CLICK HERE.

Once you have measured yourself, take the bust measurement and print the pattern closest to your size but towards the smaller size.

Here are the finished measurements of the Proteus Cardigan Pattern.

  S M L XL 2XL
Bust 33″ 37″ 41″ 44″ 48″
Waist 39″ 43″ 47″ 51″ 55″
Hem Width 63″ 67″ 71″ 73″ 77″

Step Two: Choose the pattern you will alter

Here are the patterns you can use today, they are free and available on our site with a step-by-step tutorial.

Increasing a pattern without a dart:

Increasing a pattern with a dart:

Making a full bust adjustment is easier when the pattern already has a dart.  For this technique, you can use the following patterns.

Step Three:  How to choose the right size pattern

You will need the Chest (2) Bust (3) and Under Bust measurements (4) to determine what method you will use.  Write your measurements in the spaces provided.

Step Four:  How to choose the right method

As a rule, it is better to use a smaller size than to try to make something smaller from a bigger size.  This is at a pattern level, of course.  The reason has to do with the shoulder length and the armscye length.

If you only require the bust alteration you can use the Slash and Slide Method.

If your measurements are 2″ to 6″ different and you require multiple adjustments, use the Pivot and Slide Method.

Full Bust adjustment using the Slash and Slide Method

For those with a dart who only need to increase by 2″ or less:

  1.  Trace the pattern on a large piece of pattern-making paper.  Tape the front line to the pattern paper.
  2.   Located the center of the dart and trace a horizontal line in the middle of the dart to the apex of the bust. (refer to your chart)
  3.   Trace a line from the apex to the shoulder roughly in the middle of your shoulder.
  4.   From the point of the dart trace a straight line to the hem.
  5.   Cut from the hem to the apex to the shoulder but not though, (do not cut the pattern in two)full bust adjustment
  6. Spread the pattern by half of the measurement you need.full bust adjustment7. Trace the new line of the pattern, I have marked the side with the blue dotted line.  Pay special attention to the new shoulder line when the pattern was spread the line was no longer straight. Tape the top of the right-hand side of the pattern then slash the bust dart in the middle to the apex but not through.
    full bust adjustment8. Move the pattern right the amount needed, marked below in red. Trace a vertical line from the front edge to the cutting line in the middle marked by the red small arrow, separating the grey area from the pattern.full bust adjustment9. Slide the grey area to meet the hem(red area) tape the pattern and retrace the new lines.  Move the dart up or down depending on your needs. All that remains to do is to retrace the new pattern.  Noticed how the armscye never changed nor did the width of the shoulders. However, the bust dart area and underbust have increased.full bust adjustment

For those without a dart as in the Proteus Cardigan for an increment of the bust 2″ or less: A and B Cup

This alteration is almost the same as above except we are not concerned with the bust dart. Find the location of the apex of the bust for this whether you pin the pattern to your body or if you have made a mock-up you will drape this on your shoulders. Mark the apex on the pattern and make a cut from the seam allowance

full bust adjustment
full bust adjustment

Mark the apex on the pattern and make a cut from the seam allowance stopping 1/2″ from the apex. Trace a line from the hem to the apex and from the apex to the armhole and another line to the shoulder, roughly two inches from the shoulder edge. 

Cut from the hem to the armhole but not through meaning do not break the piece apart.  Then cut from the apex to the shoulder also not breaking the pattern piece apart. Spread the pattern.  Repeat steps 7, 8, and 9, it is the same method from here on.

Full Bust adjustment using the Pivot and Slide Method

This method is for people who have a difference between 2 to 6″ between the chest and the bust and require multiple alterations such as in the case of a par shape woman with a large bust.

full bust adjustment

Place a large piece of paper on your work table and place your pattern on top of the paper.  Trace the hole pattern and using a tape measurement or ruler mark the amount the pattern needs to be enlarged in relation to your body measurements. Place a pin on the corner of the armhole, and pivot the pattern towards the markings you have previously made. Trace the new seam allowance from the pin, the side, and towards the hem.  Where the hemlines intercept, make a small notch.  I am showing you the position with the red arrows on the right. Trace the whole hemline and a few inches of the front seam allowance.

full bust adjustment

Return the original pattern to the starting position and slide down the pattern to retrace the front until it meets with the newly traced line indicated above by the blue arrow.  You will have to trace the new hemline between the blue arrow and the original traced pattern.

full bust adjustment
full bust adjustment

The front has gotten longer in the new pattern to accommodate a larger bust, but the side seam, shoulder, and shoulder width have not changed.

Whichever method you use, it will give you a larger size without changing the shape of the garment. Any questions, send them in as a comment below.

As always it would be most helpful if you just snap a pic and attach to your comment if you have something specific to look at.  That always makes it easier to respond.

Until next time!


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