High Bust vs Full Bust: The First Step to Choosing Sewing Patterns
The Pattern Size Trap No One Warns You About. You’ve measured your full bust, picked your pattern size, and carefully sewn your muslin. But when you try it on, it’s a mess: the shoulders droop, the neckline gapes, and the fit is somehow both tight and baggy. Sound familiar?
If you’ve ever felt like commercial patterns weren’t made for your body, you’re not wrong. Most traditional and vintage pattern sizing assumes a “standard” bust — usually a B cup with only about a 2-inch difference between high bust and full bust. But for those of us with larger busts or plus-size frames, that assumption breaks everything.
The fix? Stop measuring your full bust first — and start with your high bust. Here’s why it makes all the difference.
Step one: What Your High Bust Really Measures
The high bust is taken just under the arms, above the fullest part of the bust. It’s your ribcage, shoulder width, and upper chest — basically, your frame.
Think of it as the scaffolding that holds up everything else. It doesn’t change much with bra size or body fluctuations. That’s why starting here gives you a more stable base when choosing your size.
Choosing your pattern size based on high bust keeps the garment’s structure — especially around the shoulders, neckline, and upper back — aligned with your body’s architecture.
Visual tip: Align your tape snugly under your arms, not across the bust.
Eureka Moment: Start with your high bust to match the pattern to your frame, not just your chest.
Step Two: Full Bust: The Volume on Top of the Frame
The full bust measures the fullest part of your chest — often across the nipples. It includes your breast volume, which varies widely even among people with the same high bust.
This measurement tells you how much extra room your garment needs in front. But here’s the kicker: if you choose a pattern size based on this alone, everything else will be too big.
That’s how you get necklines that fall open and shoulders that slide off — the pattern was drafted for someone whose entire upper torso was that measurement, not just their bust.
If your full bust is more than 2″ bigger than your high bust, don’t skip this step.
Eureka Moment: Your full bust tells you how much extra room your chest needs , not what size to start with.
Step Three: Frame First, Volume Second: How to Pick Your Pattern Size
* First, choose your pattern size based on your high bust.
* Then, compare your full bust to the pattern’s full bust in that size.
* For fitted or very fitted designs if the difference is over 2″-3″ (5 -7.5 cm), and the pattern maker grades for a B cup you may need to do a Full Bust Adjustment (FBA).
This lets you keep the shoulders, neckline, and back fitting properly — and just expand the front where it’s needed. It’s like tailoring a jacket to your frame, then padding out the front with just enough ease for your bust.
Key Insight: High bust picks your size. Full bust tells you what to adjust.
Find Your Sewing Cup Size
Why This Matters for Plus Sizes and Bigger Busts
Most commercial pattern guides assume you know this already, which is why beginners feel like they’ve missed a secret chapter. When you change your mindset — skeleton first, volume second — you stop blaming your body and start fixing the draft.
It’s not you that’s wrong. It’s the shortcut sizing instructions that skipped over the actual architecture.
When Your Bust Is Larger (or Smaller) Than Standard
If you’re plus-size or busty, your full bust can be much larger than your frame. That’s not a problem, unless your pattern is based on the wrong measurement.
Using the high bust ensures your fit starts with your real proportions, not some industry standard-size. It also avoids the “boob tent” effect: excess fabric in all the wrong places.
My system works differently. Size Group A (US 2–18) is drafted with a generous B/C cup built in. Size Group B (US 18–34) is drafted with a D/E cup as the base. That means you’re already starting closer to reality — no need to fight a flat-front draft just to get basic curves.
Still, everybody is unique. So here’s the golden rule: choose your size by high bust. This locks in the shoulders, neckline, and back to your frame. Then, if your bust is fuller or smaller than the built-in draft, you can:
✽ Use a Full Bust Adjustment (FBA) or Small Bust Adjustment (SBA) to fine-tune volume
✽ Or, where available, select the pattern’s alternate cup-size piece for the front bodice.
Basic Rule of Fit: Start from the top down, then adjust outward from the center vertical lines. Think of it as sketching your frame first, then shading in the curves.
Guides assume you know this already, which is why beginners feel like they’ve missed a secret chapter. When you change your mindset — skeleton first, volume second — you stop blaming your body and start fixing the draft.
It’s not you that’s wrong. It’s the shortcut sizing instructions that skipped over the actual architecture.
Full Bust Measurement
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 guidelines, 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
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.
High Bust Measurement
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
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.
o 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.
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
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 they are vintage, modern, daywear or evening glamour.
A better fit will make you feel great!
