# Bra Size Converter: Translate Global Sizing Systems Instantly
Buying lingerie online is a minefield. A 36C in the US isn't the same as a 36C in the UK, EU bands run differently, and Australian sizing throws another variable into the mix. Multiply that by cup shape, sister sizing, and brand-specific fit quirks, and you've got a category where the wrong size is the rule rather than the exception.
The Bra Size Converter on TinyToolbox cuts through that confusion. It's a free, browser-native tool that translates band and cup measurements between the four major regional sizing systems in one click. No accounts, no ads, no "upload your photo for a fit estimate" gimmicks. Just clean conversion math you can verify against a measuring tape.
What the Bra Size Converter Actually Does
The tool takes your band measurement (the number, in inches or centimeters) and cup size (the letter) and returns the equivalent size across US, UK, EU, and AU systems. It also handles the most common fitting inputs: band circumference in inches or cm, and cup letter (A through roughly L depending on band).
Under the hood, it's doing what every fit specialist does manually: mapping your band number to the regional base system, then applying the appropriate cup-letter offset. UK and US use the same cup progression (A, B, C, D, DD, E, F, FF, G...) but the band numbering differs by one step in some ranges. EU uses centimeters for the band directly, which is why a "75" in France is not a "75" anywhere else. Australia typically aligns with UK sizing.
The converter handles those offsets so you don't have to memorize them.
Why This Matters More Than You'd Think
Sizing inconsistency isn't a minor inconvenience. It's the reason returns account for roughly 30% of online apparel purchases, and lingerie is the worst offender. If you've ever ordered a bra in your "usual" size from a different country and gotten something that fit like a costume, you've felt the gap.
The math is also unforgiving. A 1-inch band error can mean the difference between a supportive fit and one that rides up your back all day. Cup-letter shifts in UK vs US (where D becomes DD at the same actual volume) compound the error. A reliable converter eliminates the guesswork at the most important step: knowing what size to put in the search box.
Four Real-World Use Cases
1. Cross-Border Shopping
This is the obvious one. You're browsing ASOS (UK), ThirdLove (US), and Intimissimi (EU) in the same afternoon. Each site defaults to its own regional sizing. The Bra Size Converter lets you punch in the size you already know fits and get instant equivalents across all four systems, so you can filter on the right size on every storefront.
2. Verifying a Tape-Measure Self-Measurement
If you've measured yourself at home, you have two raw numbers: band circumference in inches or centimeters, and bust circumference. The converter can take your band measurement directly and show you what cup size corresponds at that band in each system. Pair this with our Length Converter if you're working between inches and centimeters and want to double-check the conversion math.
3. Decoding Vintage or International Listings
Shopping secondhand on Poshmark, Depop, or eBay often means decoding sizes from Japan, France, or Italy. The converter turns a confusing "85C" or "EU 70B" into a familiar US/UK size in one step. Useful for resale buyers, vintage collectors, and anyone whose dream bra exists only in a 1985 French catalog.
4. Sizing for Custom or Independent Brands
Many indie lingerie makers publish sizing in a single system (usually EU) and assume you'll know how to translate. The converter is faster than emailing customer service and more reliable than a Reddit thread from 2019.
Pro Tips for Getting the Right Size Every Time
Measure your band snug, not tight. The band should be parallel to the floor, exhaled but not sucked in, snug enough that it stays put when you lift your arms. If the converter output doesn't match what you usually wear, your measurement is the variable, not the tool.
Know your sister size. If a 34C fits in the cups but the band is slightly loose, your sister size is 36B (one band up, one cup down, same cup volume). The converter's output can hint at this if you cross-reference your usual size with the equivalent in another system.
Cup volume ≠ cup letter across systems. A US D and a UK D are the same cup volume, but a US D is a UK D (no shift). The shift happens at DD/E in some brand guides, which is where most people get tripped up. The converter handles this so you don't have to memorize the table.
Weight changes invalidate your old size. If you've gained or lost more than about 10 pounds, your old size is probably wrong. Re-measure, then run the converter fresh. The Weight & Mass Converter is useful for tracking changes in pounds vs kilograms if you're logging progress across regions.
Trust the tool, not the brand chart. Brand charts are often wrong or aspirational. The converter is based on the ISO and regional standards, not on what a particular marketing team decided to call a size.
How It Stacks Up Against Doing the Math Yourself
You can absolutely memorize the US/UK/EU/AU conversion table. It fits on an index card. But you'll still make errors under time pressure, you'll second-guess the cup-letter shift at DD/E, and you'll have to recalculate every time you're shopping. The converter is the same logic, just faster and harder to typo. It's the kind of tool that pays for itself the first time it saves you a return shipping label.
FAQ
Is the Bra Size Converter accurate for all cup sizes?
It covers the full standard range (A through roughly L) across US, UK, EU, and AU systems. Specialty sizes beyond standard ranges (AAA, beyond L, maternity-specific cuts) may not be supported in every system.
Does the tool store my measurements?
No. Everything runs in your browser. No data is sent to a server, and closing the tab clears the input.
Can I convert from centimeters to inches, or do I need a separate tool?
The converter accepts band measurements in either inches or centimeters directly. If you're working with a measurement in a less common unit, use the Length Converter to convert first, then run your band value through the Bra Size Converter.
Conclusion
Bra sizing is one of those problems that looks trivial until you actually try to shop across regions. The math isn't hard, but the cup-letter shifts, the band numbering differences, and the EU centimeter system together create exactly the kind of friction that leads to wrong-size purchases and expensive returns. The Bra Size Converter handles all four major regional systems in one click, runs entirely in your browser, and doesn't ask you to create an account or upload a photo. Bookmark it before your next cross-border lingerie order, and you'll save yourself at least one return shipment this year.