Tomima Talks: Do You Need A New Bra Size?
- Tomima
- 2 days ago
- 4 min read
By Tomima Edmark, Founder & CEO of HerRoom
Originally published January 14, 2021 — Updated for today
If your bras no longer fit the way they used to, the problem is rarely the manufacturer. It’s almost always a size change.
After more than 20 years in the lingerie industry—and fitting tens of thousands of women—I can say this with confidence: most women are wearing the wrong bra size, and many don’t realize it because they’ve never experienced a correct fit.
Bra sizing isn’t intuitive. But once you understand how band size, cup size, and volume actually work together, finding your correct size becomes straightforward.
How to Change Your Bra Band Size Correctly
When you need a larger band size
If your newest bra feels tight even on the loosest hook, your band size is too small.
Here’s the rule many women miss:
When you go up a band size, you must go down a cup size to keep the same cup volume.
Example:
38D → 40C
Skipping this adjustment causes cups to feel too large and unsupportive.
When you need a smaller band size
Fasten your newest bra on the tightest hook and raise your arms overhead.
If the band rides up your back, it’s too large.
Here’s the corresponding rule:
When you go down a band size, you must go up a cup size to maintain volume.
Example:
38D → 36DD (D2)
Failing to increase the cup size is why downsizing bands often feels “uncomfortable” or “too tight in the cups.”
For a more in-depth explanation on band sizing, click here.
How to Know If You Need a Larger Cup Size
The most common signs your cups are too small:
Breast tissue spilling over the top or sides
The center panel (gore) not resting flat on your sternum
Each cup size represents approximately one inch of bust circumference, but that inch matters differently depending on your band size.
Bands 28–36: one inch is significant
Bands 38 and above: one inch is proportionally smaller
This is why women in larger band sizes often need to increase more than one cup size to achieve proper containment.
Correct fit indicators:
All breast tissue contained
Center panel rests firmly on the sternum
When determining your true cup size, avoid plunge bras, wireless bras, bralettes, and minimizers. These styles are not designed for precision fitting, and minimizer bras are not meant to tack at the center.
Why Cups Often Fit First—and Bands Second
Once your cups fully contain your breast tissue, many women find their band suddenly feels too loose. This is expected. Breast tissue that was previously escaping into the band area is now properly supported in the cups.
Remember the rule:
Down a band → up a cup
Example:
40DDD (D3) → 40H (D5)
Band now too large → 38I (D6)
When Cups Are Too Large
Wrinkling or empty space in the cups—after scooping and adjusting—means the cups are too large. If tightening straps doesn’t resolve it, move down one or two cup sizes.
For a more in-depth explanation on cup sizing, click here
The #1 Bra Sizing Mistake Women Make
The majority of women wearing the wrong bra size are wearing:
A band that is too large
Cups that are too small
This stems from outdated manufacturing limits, cultural stigma around larger cup sizes, and widespread misunderstanding of what proper bra fit actually looks like.
Cup sizes above a D do not automatically mean “large breasts.” They often mean correctly fitted breasts.
To see an actual example of a model starting in a 34G(D4) and finding she’s a 30I(D6), watch this short video.
What Are Sister Bra Sizes — and When Not to Use Them
Sister sizes are bra sizes that share the same cup volume but have different band sizes. They are useful only as a temporary diagnostic tool when fine-tuning fit.
If your bra almost fits, one of your sister sizes may help you identify whether the issue is in the band or the cups.
However, this is critical to understand:
Once you establish your correct bra size, sister sizes should not be used as substitutes.
A sister size does not fit as well as your true size, particularly for women with smaller cup sizes. On smaller frames, even slight shifts in band tension or cup proportions noticeably affect support, shaping, and comfort.
Sister sizing is meant to:
Help troubleshoot fit issues
Confirm sizing direction
It is not meant to:
Replace your actual size
Be worn long-term
For best results, use sister sizes briefly, then return to your confirmed bra size for optimal fit.
For a more in-depth explanation of sister sizing, watch this short video.
Use HerRoom’s Fitting Room for Professional-Level Guidance
As an ecommerce retailer specializing in bra fit, HerRoom has built The Fitting Room—a comprehensive educational resource designed to help women find their correct bra size with confidence.
The Fitting Room includes:
In-depth fit guides
Educational videos
Expert-written blogs
Visual examples of correct and incorrect fit
It is one of the most extensive bra-fitting education libraries available online and is accessible anytime, from anywhere.
If you want to understand your bra size—not just guess at it—the Fitting Room provides the tools and expertise to get you there.
Final Expert Advice
When testing a new bra size, always start with a proven, consistent bra style. Over two decades in the lingerie business have shown me which designs perform reliably, with low return rates and high customer satisfaction.
A well-fitting bra changes everything—from comfort to confidence. And once you know your true size, you’ll never go back.
Tomima Edmark
Founder & CEO, HerRoom
