Measuring to Find your Sewing Bust Cup Size

A dress sewing cup size diagram. Learn to sew inclusive size vintage, everything from full bust adjustment on vintage patterns
Diagram 1

Before you start making any adjustments to the bust in your sewing patterns, let’s make sure you know how to measure to find your sewing bust cup size accurately and use this to determine your sewing cup size.

Don’t worry, it’s easy-peasy!

You’ll need two measurements to figure out your sewing cup size: your full bust and high bust. To measure your full bust, stand in front of a mirror and make sure your tape measure is parallel to the floor. Your high bust is the area right below your underarms.

To get your sewing cup size, simply subtract your high bust measurement from your full bust measurement. 


 Keep in mind that this size is only for sewing, and not for bra fitting.

The Secret to Finding Your Sewing Cup Size

diagram for finding bust cup size
Diagram 2

To find your sewing cup size you simply subtract your high bust measurement from your full bust measurement.

So a high bust of 36 and a full bust of 39 = 3 inch difference

 The general rules for sewing cup sizes are as follows. 
These are basic rules and not the law! 

1 inch (2.5cm) difference = A cup

2 inch (5cm) difference = B cup

3 inch (7.5cm) difference = C  cup

4 inch (10cm) difference = D cup

5 inch (12.5cm) = DD cup

6 inch (15cm) = E/F cup

7 inch (17.5cm) = G/H cup

An image showing a side view of how to take a full bust measurement

It’s essential to take the full bust measurement wearing the same bra or undergarment to be worn with the dress.

Different bras can affect the shape and height of breasts, impacting the fit of tight, non-stretch fabrics.

While this is less critical for casual and stretchy clothing, accurate measurements are still recommended. Wear the same undergarment for the best results.

An image depicting the steps for how to measure dress bust cup size showing how to measure a high bust

Measuring your high bust is a reliable way to determine your frame size, regardless of your breast cup size.

The measurement captures your back, shoulders, and chest width, so it’s essential to measure it accurately.

If your bust size is more significant than your frame size (Large breasts and small frame). Then it’s best to choose a pattern based on the high bust measurement. You can then make adjustments to the front pieces accordingly.

This approach ensures that the garment fits well across the shoulders and upper back. This will create a flattering and comfortable fit.

Why dress cup size is not the same as bra cup size

An image depicting the steps for how to measure dress bust cup size showing a side view

The dress cup size is not the same as bra cup size. When measuring for a bra the aim is to calculate the volume of your breasts and fit them into a supporting cup.

A dress cup size is calculating how much your breast curves out from your body. Diagrams 3 at the bottom of this page show side views explaining this.

As your dress bust cup size increases the distance the breasts curve out from your body also increases. Therefore the garment will pull tight across the bust line too.

When you learn how to check and adjust your pattern to fit your body shape, you gain the power to confidently adjust any pattern to fit you perfectly.

As a result, you can create garments that fit and flatter your body. Making you feel confident and proud of your creations.

An image depicting the steps for measuring dress bust cup size and body length is provided.

When measuring from your high shoulder point, over the full bust down to your waist, the distance increases. So this increase will occur as your cup size goes up.

Therefore, a garment will ride up if the dress cup size is too small.

Why your Full Bust Measurement is So Important

Diagram 3

If your full bust measurement is more than 3 inches (7.5cm) larger than your high bust, we recommend purchasing the dress pattern that best fits your high bust measurement and then making a Full bust adjustment on the pattern.

This way, the pattern will fit your neck, shoulders, back width, and armholes much better, and you can easily adjust the bust to your size.

Diagram 3 shows how the front body length increases or decreases when your bust size is larger or smaller than the pattern is graded for.

Keep in mind that most original vintage patterns are designed for a B – C cup maximum, so you may need to adjust the pattern accordingly.

No need to worry, though! Our full bust adjustment tutorial will guide you through the process, helping you achieve the perfect fit by adding fullness where you need it without distorting other parts of your pattern

jane russel cup size 1080

Understanding that your dress sewing cup size may differ from your bra cup size can help avoid confusion.

Dress sizes have changed over the years to appeal to vanity and increase sales. This means that what was once a size 20 in the 1950s may now be a size 14. Similarly, a DD cup bra from one brand may be equivalent to an H cup in another brand.

However, sewing cup sizes are much simpler and more consistent across different pattern publishers, as they are based on actual human body proportions. Once you determine your sewing cup size, it will remain constant across patterns.

Don’t worry if this seems complicated at first. It’s actually straightforward, and making a few bodice templates in basic designs can help you compare them easily with new patterns you buy.

Remember, the most important thing is to get the best fit for your body shape and feel proud of your creations, whether vintage or modern, daywear or evening glamour. A better fit will make you feel great!”

Bust position and shape can have a direct effect on your dress cup size, but don’t worry, it’s not too complicated. Different bras like uplift bras or 1950’s pointed bullet bras can give two different shapes and measurements to your full bust line. So, it’s important to take your measurements wearing the undergarment you plan to wear with the final dress.

It’s worth noting that most vintage sewing patterns were drafted for a B cup or small C cup at most and will require a full bust adjustment for larger cup sizes. But don’t let that discourage you! We have a great resource available to help you make those adjustments and achieve the perfect fit for your body shape.

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