Methodology · last reviewed 2026-05-28
How we translate bra sizes across brands
A 34DD is not the same garment in every brand. BraFinder maps 33 brands to a neutral reference size, each with a documented offset and a confidence score, so we can convert your size from any brand into any other. No brand's thumb on the scale. Here is exactly how it works.
The method, in four steps
We never translate one brand's label directly into another's. We always go through a neutral reference size in the middle. That is what keeps the translation brand-neutral and consistent in both directions.
- 1
Read your size and the brand it's in
Start from a size you know fits, in the brand you bought it in (for example, a 34DD in Victoria's Secret). If you only know a plain US size, that works too.
- 2
Remove that brand's offset to get a neutral reference
Every brand is mapped to how it runs versus a neutral US reference: a band or cup that runs large or small by a documented amount. We strip that brand's offset out so we're left with your true, brand-independent size.
- 3
Apply the target brand's offset and sizing system
We add the target brand's offset back in and convert into its sizing system (US, UK, or EU cup letters differ above a D cup). Differences smaller than a full size show up as a fit note, not a changed label.
- 4
Return the size, with a confidence score and a fit note
You get the size to buy in that brand, a 0–1 confidence score reflecting how well-evidenced the offset is, and a plain-language note on how the brand tends to fit.
A worked example
Say your true size is a 34D.
- In Victoria's Secret, whose cups run a full cup small, we move you up to 34DD.
- In Wacoal, which is true to size, you stay at 34D.
- In Panache (UK sizing), it switches you into UK cup letters for the same volume.
Half-step differences (a band that runs slightly snug, a cup slightly generous) show up as a fit note rather than a changed label. Try it with your own size →
How each brand runs
The offsets that drive every translation, grouped by how the brand behaves. This is the proprietary table BraFinder maintains and the reason a neutral, cross-brand answer is possible at all.
True to size
The size on the label matches a neutral reference. Start at your usual size.
Wacoal, Panache, Fantasie, Glamorise, b.tempt'd, Maidenform, PrimaDonna, Marie Jo, Anita, Gossard, Goddess
Cups run small — size up
A cup holds less volume than the label suggests. Go up a cup (a full cup for the worst offenders).
Victoria's Secret (a full cup), Natori, Chantelle, Simone Perele
Cups run generous — size down
A cup holds more than the label suggests. Consider going down a half cup.
ThirdLove, Elomi, Under Armour, Nike
Bands run snug — size up the band
The band is tighter than the number implies. A bigger band number (or its sister size) sits more comfortably.
Freya, Calvin Klein, Curvy Kate, Brooks
Bands run loose — size down the band
The band is looser than the number implies. A smaller band number holds better.
Bali, Playtex, Cacique, Torrid, Vanity Fair, Triumph
Sized by their own chart
These brands use XS–XXL, numeric, or adjustable sizing instead of band + cup. We point you to the brand's own chart rather than translate a band/cup.
SHEFIT, Kindred Bravely, ENELL
How confident we are, and how that improves
Every offset carries a confidence score from 0 to 1, and we show it on each translation. We are honest about the stage each number is at. Right now every offset is at the first tier: a starting estimate, not yet validated against real fit outcomes. As shoppers tell us how a recommendation actually fit, offsets move up the tiers and the confidence rises.
1. Chart-derived
~0.35–0.7Built from published brand size charts and documented fit behavior. A reasoned starting point.
Where our offsets sit today (v1-2026-05-28)
2. Community-corroborated
higherCross-checked against measured garment data and aggregated fit feedback.
3. Outcome-backed
highestConfirmed by real fit outcomes shoppers report back to us.
Brands that size by their own XS–XXL or numeric chart (rather than band + cup) carry the lowest confidence by design, because there is no band/cup to translate. We send you to the brand's own chart instead.
Brand-neutral by construction
The translation is math over a fixed offset table. It does not know or care which brands pay us a commission. No brand can buy a better size or a higher place. See our affiliate disclosure.
Maintained and dated
The offset set is versioned (v1-2026-05-28) and last reviewed 2026-05-28. When a brand changes how it drafts, the offset changes here. Found one that's off? Tell us and we'll review it.
Related
Common questions
Why does my bra size change so much between brands?
Because there is no enforced standard. Each brand drafts to its own block, so a band can run snug or loose and a cup can run small or generous by a full size. UK and EU brands also use different cup-letter sequences above a D cup. A 34DD in one brand is genuinely a different garment from a 34DD in another, which is why a neutral translation is needed rather than a single number.
How does BraFinder translate a size across brands?
We map every brand to a neutral reference size with a documented offset (how its bands and cups run) and a sizing system. To translate, we remove the source brand's offset to recover your true size, then apply the target brand's offset and convert cup letters into its system. BraFinder maintains offsets for 33 brands.
Are these offsets measured or estimated?
Today they are starting estimates derived from published brand size charts and documented fit behavior, not yet from measured fit outcomes. Each offset carries a confidence score, and they are designed to be corrected over time as real fit results accumulate. We label this openly rather than present estimates as measured fact.
Do affiliate relationships affect the sizing?
No. The size translation is math over a fixed offset table and does not consider which brands pay a commission. BraFinder is brand-neutral by design: no brand can buy a better translation.
Translate your size into any brand
Enter a size you know fits and see it in every brand we track, with a confidence score and a fit note. Free, no account.