How to know if you need a bust adjustment – 3 simple ways


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You just finished sewing your shirt.

It didn’t turn out the way you expected at all.

Looking in the mirror you notice bubbly wrinkles all over your chest and when lifting your arms the shirt pulls up from your jeans.

Did you mess something up? Maybe cut the fabric wrong or missed the seam line while stitching?

You’re sure you were extra careful choosing size this time. Can it be that you need a bust adjustment? How do you know if you need one?

Can you relate?

Time to learn the Full or Small Bust Adjustment, my friend 🙂

Don’t fret, it’s not as complicated as it seems. 

Common advice tells you to make a Full Bust Adjustment if your cup-size is larger than B. 

My take? You may not need one. 

Here’s 3 different ways to figure out if you do, and how to take your measurements and calculate how much. So you can make a confident decision next time you sew. 

But before you can figure out if you need to do this bust adjustment on your pattern, let’s talk about why you’d want one in the first place.

What is a bust adjustment?

A full or small bust adjustment is an alteration done to your pattern or test garment before you cut and sew the fabric you plan to use for the actual garment.

Why make a bust adjustment?

When your bust circumference differs more than one cup size, smaller or larger, to the cup size used when the pattern was drafted, the garment will not fit right.

Above all, the goal with a bust adjustment, is making enough room for your bust so the garment sits where intended by the designer as well as you being able to move around freely.

Sometimes you actually can get away with not doing anything at all. But, if your pattern is somewhat shaped to the your body’s silhouette, it’ll be obvious if you haven’t made one. 

3 reasons why considering it, despite the extra prepping time:

  1. Visual: avoid shirt gaping
  2. Practical: allow for arm mobility 
  3. Comfort: move around easily
shirt gaping example
An obvious case of missed bust adjustment

When to use a bust adjustment?

Most commonly it’s used for a fitted or semi-fitted top like a blouse or a shirt. It can also be used for a t-shirt or a jacket, with or without darts.

Do you always need a bust adjustment?

The answer: It depends.

General exceptions from “the bust adjustment rules” are tops or shirts with more than 12 cm / 5 inches of ease (i.e. the difference between your body’s and the garment’s bust measurements.) A loser design allows for flow and movement and doesn’t need a lot of shaping.

However, even boxy tops may need a bust adjustment.

Also, different brands draft patterns with different cup size increments, usually between 4-6 cm / 1.5-2 3/8 in.

So if you’re going for a good fit, you have to make the calculation anyway.

Getting prepared

Firstly, you need the pattern’s cup-size.

When buying a new pattern you should find the information on the patternmaker’s site, in the product description or size chart.

If you already own the pattern, look for the information in the instructions or directly on the printed pattern. 

Secondly, you need your own measurements. 

Don’t confuse pattern cup sizes with bra manufacturer’s cup sizes, they’re not the same. 

Simplified, a bra manufacturer’s cup sizes is based on your full bust measurement and your under bust measurement. 

In a sewing pattern, cup-sizes are based on your full bust measurements minus your high bust measurement. The difference is rounded up to inches ( 2.5 cm increments) per cup size.

Like this:

Cup size calculation chart

Pick the cup size closest to your measurements. If you fall exactly between two, select the larger one. It’s easier to remove fabric than to add, once you’ve cut your fabric.

Why not just go for a bigger or smaller size?

By choosing a different size, your garment will change proportions. For example, the shoulder width and back width but also the neck width and neck depth as well as the armhole. Those key points all affects the bust fit. 

You may get away with choosing a different size, if you’re a C cup and the pattern brand drafts for a B cup. But a difference of more than one cup size can affect other parts and consequently give you more things to alter than is necessary.

Even if you have the same bust measurements as the pattern, it’ll show on your back, shoulders and armhole on a fitted garment. 

If the pattern you’re sewing offers different cup sizes it’s clearly stated on the pattern envelope or cover. But even if they do, you may have to adapt it to your body anyway. 

The simple reason is that we all look different for example high or low bust line, narrow or wide bust apexes, or full or hollow chest. So make sure you double check the finished measurements, as well as the suggested fit, on all patterns you’re about to sew.

Measurements you need


Measure around your body across your bust.

high bust
High bust measurement


Measure around your body, over your bust. 

full bust
Full bust measurement


Inner shoulder point to apex so you know where to mark the apex on the pattern vertically. 

Note: There are several ways to take this measurement. The simplest one is to wear a t-shirt or a tank top, start measuring from the shoulder seam closest to your neck down to your bust apex. 

This doesn’t require any calculations or considerations of the back neck measurement and you can measure the equivalent distance directly on your front pattern piece and mark with a pencil.

bust height
Bust height measurement


To know where to mark the apex on the pattern horizontally (between the center front and the armscye) measure between your bust apexes.

apex width
Apex width measurement


Optional. Measure from side seam to side seam across your bust. This is to know the distribution of your measures between front and back e.g. if you have a broad or narrow back compared to the pattern.

bust width
Bust width measurement



  • Subtract your full bust measurement from your high bust measurement and calculate your cup size.
  • Find information about the pattern brand’s cup sizes and their size chart.


If the pattern match your cup size and bust measurement, pick a size and start sewing.

Or, if the pattern measurements and cup size differ from yours, make a note.

  • Find the ready garment measurements.
  • Subtract your bust measurements from the ready garment bust measurement.


Now you have your basis for deciding whether you need to make a bust adjustment.


3 ways to decide if you need a bust adjustment

Method 1 – Gauging

The least complicated way

Consider the ease in the garment design based on the cover image and pattern measurement charts. If you’ve tried this brand before, and got a great fit, chances are you’ll succeed with this pattern too. 

If the brand is new to you, have a look online and see if you can find others that have sewn it before you. Look at their images and decide if you like the way their garments fit on them. Make changes to your pattern according to your findings.


Method 2 – Calculating

The most scientific way

Compare your notes and the finished garment measurements chart provided by the pattern company. Decide if you want to make the changes needed to match the pattern to your body or if you’re going to skip it.


Method 3 – Testing

The most practical (and closest to the truth) way

Sew the garment with the original pattern pieces. Try on the test garment and cut/pin the fabric to accommodate to your measurements.

This method requires that you already own the pattern and are comfortable with transferring alterations from your muslin to your pattern. 

If you’re new to bust adjustments it’s best to start with method number two.


Next step

When you’ve decided which method to use, there are 4 different bust adjustments to resolve the difference between the measurements you have, and the measurements you need; 

  • Bust adjustment with no dart
  • Bust adjustment with bust dart
  • Bust adjustment with waist dart
  • Bust adjustment with princess seams

These are topics for upcoming posts.


Time for some action

So, now you know how to take your measures and determine if you need to make a bust adjustment or not.

You also know it differs from pattern to pattern and that the decision is based on the garment design, ease and finished measurements compared to your body.

 To take your new skills into practice, make a habit to take your measurements regularly and keep them close by when you’re sewing.

I’ve created a checklist for the most needed measurements you need.

Download it here and keep it nearby next time you sew.

 Sew great!

Get the Better Fit checklist

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