Brand Size Decoder
Your size is not a single fixed label. The same body is a 34C in US sizing, a 34C in UK sizing, an 85D in EU sizing and a 100D in French sizing — and brands add their own quirks on top. The Brand Size Decoder translates your usual size into the sizing system of 12 major brands, shows your sister sizes in that system, and explains what each brand's system means, so you stop guessing when you shop across brands.
Decode Your Size
Sizes on this page are estimates. Sizing varies by brand and style, so always check the brand’s own size chart and try on before you buy. Nothing here is medical advice.
How decoding works
Decoding is a two-step translation. First, the decoder reads your size as a body, not a label: your band number becomes an underbust measurement, and your cup letter becomes a bust-to-band difference. Second, it re-labels that same body in the brand's system — a new band number by that system's band rule, and a new cup letter by its letter progression.
The math is the same method this site's main calculator uses, so decoder results and calculator results always agree. One worked example: a US 34C means a 34-inch underbust and a 3-inch difference. In EU sizing the band rounds to the nearest 5 cm (85) and the third cup letter is D, giving 85D. In French sizing the band adds 15 to the EU number, giving 100D. In Australian sizing the band subtracts 22, giving 12C. Same body, four labels.
Where decoding stops
A system translation cannot capture a brand's cut. Two bras with the same label can still fit differently because of cup depth, wire width, band stretch, gore height and fabric. Treat the decoded size as your starting point, then check the brand's own chart and, when you can, try the bra on.
Brand profiles — the 12 brands in this decoder
Each brand below uses one sizing system for the lines covered here. The note explains what that means when you shop it.
Victoria's Secret — US
Uses US sizing. If you are between sizes, the brand's own chart is the final word — its styles vary in stretch and coverage.
ThirdLove — US
Uses US sizing and offers half-cup options in some styles. A half cup sits between two full cups; it does not change your band.
Wacoal — US
Uses US sizing on its American lines. Wacoal also makes Japanese lines, which use a different scale — check which line you are buying.
Glamorise — US
Uses US sizing, with a focus on fuller cups and wider bands.
Cacique — US
Lane Bryant's Cacique line uses US sizing, with plus-size bands at its core.
Nike — US
Nike sports bras often use alpha sizes (XS–XL) alongside band and cup sizes. Use the band/cup conversion as your starting point, then check the style's alpha chart.
Panache — UK
Uses UK sizing. UK cup letters run DD, E, F, FF, G, GG — so a US DDD is usually a UK E.
Freya — UK
Uses UK sizing, like Panache. Freya's plunge and balcony styles share the same UK scale.
Elomi — UK
Uses UK sizing, with a fuller-bust focus. Elomi bands run in the same UK inch numbering as Panache and Freya.
Curvy Kate — UK
Uses UK sizing. Its fuller-bust styles use the same UK cup progression as other UK brands.
Chantelle — FR
Uses French sizing. French bands add 15 to the EU number, so an EU 85 is a French 100.
Triumph — EU
Uses EU sizing: centimetre bands in steps of 5 (70, 75, 80, 85, 90) with consecutive cup letters.
Why the same size fits differently across brands
Four things vary even when the label is identical. Band stretch: some bands are made to stretch more, so a firm 34 from one brand feels like a loose 34 from another. Cup depth: a cup can be shallow and wide or deep and narrow at the same volume, which changes whether tissue sits comfortably. Wire width: narrow wires suit a narrower root, wide wires a broader one. Grading: brands scale their patterns differently as sizes increase, so fit can drift at the ends of a size range.
The practical response is always the same: start from your decoded size, check the brand's own chart, and if the cups feel right but the band does not, try a sister size before changing the cup.
Decoding in the fitting room
Start from your decoded size, then verify it on your body. Band first: it should sit level and feel snug on the loosest hook when the bra is new — that leaves room to tighten as the elastic stretches. Cups second: no spilling over the top or at the sides, no gaping or wrinkling. Gore third: the centre panel should sit flat against your chest. If all three pass, the decoded size works in that brand. If one fails, change one thing: the band via a sister size, or the cup on the same band.
If the decoded size is not sold by that brand, do not jump to a random nearby size. Use the sister sizes the decoder shows, in that order: same cup volume, different band. And note the half-cup exception — brands that offer half cups (ThirdLove is the best-known example) give you a step between two full cups, which helps when you sit exactly between sizes.
Frequently Asked Questions
Why does my size change between brands if my body has not changed?
Because the label is not a measurement — it is a size in a particular system. US, UK, EU and French systems assign different letters and numbers to the same body. The decoder translates your size between systems; it cannot account for a single brand's cut, stretch or grading, which is why the brand's own chart still matters.
Is a US DDD the same as a UK E?
Usually, yes. In the UK progression the letters after DD are E, F, FF, G, GG, while US sizing uses DDD, G, H after DD. That is why a US 34DDD normally converts to a UK 34E. The decoder uses exactly this letter mapping.
What is a sister size, and when should I try one?
A sister size keeps roughly the same cup volume while changing the band: one band down and one cup up, or one band up and one cup down. Try one when the cups feel right but the band feels too tight or too loose, or when your usual size is out of stock.
Do brands within the same system fit identically?
No. Two brands can both use US sizing and still fit differently, because cup depth, wire width, band stretch and gore height vary by design. The system tells you the label; only trying the bra on tells you the fit.
What if my converted size is not sold by that brand?
Use the sister sizes shown by the decoder. If neither sister size is available either, go back to your measurements with the main calculator and check the brand's own chart before ordering.
How accurate is the decoder?
It is as accurate as the conversion math behind it — it follows the same method as this site's main calculator, so decoder results match calculator results. It is still an estimate: brands vary, and no converter can replace trying a bra on.