tape-measure

Do you need a bust adjustment?

You just finished sewing your shirt, and 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? Or, does your pattern need a bust adjustment?

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. Let me show you 3 ways to figure out if you need a bust adjustment or not. To be sure, you need to take your measurements and make a calculation. 

But first, let’s go through some reasons 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?

Above all, the goal with a bust adjustment is to make enough room for your bust. It’s’ partly for the visual impression, so the garment sits where it’s intended. It’s also for functionality so that you can move around freely.

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

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

Why a bust adjustment can be worth the extra prepping time

  1. Avoid shirt gaping
  2. Better arm mobility 
  3. Comfort
shirt gaping example
It would have needed a bust adjustment.

When to use a bust adjustment?

Most commonly, it’s used for fitted or semi-fitted tops like blouses or shirts. However, 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 cup size information on the patternmaker’s website, in the pattern’s product description, or a size chart.

If you already own the pattern, look for the cup size 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 size is based on the full bust and underbust measurements. 

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.

Cup size chart
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. So the shoulder width and back width will differ. But the neck width and neck depth will also change, as well as the armhole. So those key points all affect 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 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, like high or low bust lines, narrow or wide bust apexes, or full or hollow chests. So make sure you double-check the finished measurements, as well as the suggested fit, on all patterns you’re about to sew.

Take your measurements

High bust 

Measure around your body across your bust.

high bust

Full bust

Measure around your body, over your bust. 

full bust

Bust height

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 it with a pencil.

bust height

Apex width

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

Bust width

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

bust width

Calculation

  1. Subtract your full bust measurement from your high bust measurement and calculate your cup size.
  2. Look for information about the pattern brand’s cup sizes and their size chart.

 

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

Or, if the pattern measurements and cup size differ from yours:

  1. First, find the ready garment measurements.
  2. Then, 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 – Estimating

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, look online and see if you can find others who have sewn the garment before you. Look at their images and decide if you like the way their garments fit on them. Then, 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. Then, 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 way (and closest to the truth).

Sew the test garment with the original pattern pieces. Then, try it on and cut/pin the fabric to accommodate your measurements.

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

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

Time for some action

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.

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

 Sew great!