Bra Size Calculator

Accuracy comes from technique, not talent. Before you measure, get four things right:

Sister sizes keep cup volume roughly constant while the band changes. Step the band down and the cup letter steps up: 32D, 34C and 36B are sister sizes with nearly identical cup volume but very different band tension. The bra size calculator shows your sister sizes for every system, because they are the fastest escape route when a size almost fits.

Use a tighter sister size when the band feels loose but the cups are perfect. Use a looser sister size when the band digs in but the cup volume is right. Each system keeps its own cup ladder — UK double letters such as DD and FF never leak into the single-letter EU or JP sequences. The bra size calculator prints each pair so the trade is explicit.

The numbers behind the method are well documented. Fitting surveys going back four decades consistently report that 70–85% of bra wearers wear a size that misses their measurements — most often a band one or two sizes too loose paired with a cup one or two letters too small. And since EN 13402 harmonised continental labelling in 2017, cross-border conversion has been stable enough to automate, which is exactly what the six-system output here does.

For measurement-to-label conversion, very accurate: the arithmetic is deterministic and each system's data comes from published size charts. For real-world fit, honestly imperfect: breast shape, root width, projection and brand patterning all move the answer by a letter or more. That is why no bra size calculator — ours included — should promise an exact size, and why every result here ships with a fit checklist.

Remeasure every six to twelve months, after any weight change, pregnancy or hormonal shift. Bodies drift, bands stretch, and a two-minute refresh with the bra size calculator keeps your starting point honest.

Three design choices make this bra size calculator worth your thirty seconds. First, transparency: every label it shows is traceable to a published size chart, and the per-system data is versioned so updates never silently change your result. Second, privacy: the bra size calculator runs entirely in your browser, so your body measurements never touch a server, an account or an analytics log. Third, honesty about limits: the tool calls its output a starting size and hands you a fit checklist, because anyone promising an exact size is overselling arithmetic. That candour is why the bra size calculator earns repeat use.

The payoff is confidence in any shop and in any bra size calculator result you read anywhere. With one pass through the bra size calculator you carry six labels — US, UK, EU, FR/ES, AU/NZ and JP — plus the sister sizes that rescue nearly-right fits. Bookmark the bra size calculator, re-measure twice a year, and let the chart pages do the rest — a bra size calculator this transparent earns its place in your routine.