Convert bra sizes across US, UK, EU, and AU charts, then compare sister sizes and fit notes before you buy. Use it to test different inputs quickly, compare outcomes, and understand the main factors behind the result before moving on to related tools or deeper guidance.
Last updated
Chart conversion only
Bra sizes do not translate perfectly across brands. This page converts common label systems and shows same-system sister sizes, but actual fit can still change because cup shape, wire width, and brand grading vary.
What sister sizes mean
Sister sizes keep roughly the same cup volume while changing the band. Going down one band usually means going up one cup, and going up one band usually means going down one cup. They can help when the cup feels close but the band tension is wrong.
Bra-size conversion
US 32C
Equivalent labels across common systems, plus same-system sister sizes when they exist.
Source size
32C
Systems shown
7
Sister size down
30D
Sister size up
34B
International bra-size sheet
System
Equivalent size
Notes
US
32C
Original selected system.
UK
32C
Label equivalent only — fit can still vary by brand and style.
EU
70C
Label equivalent only — fit can still vary by brand and style.
AU/NZ
10C
Label equivalent only — fit can still vary by brand and style.
FR/ES
85C
Label equivalent only — fit can still vary by brand and style.
IT
2C
Label equivalent only — fit can still vary by brand and style.
JP
70C
Label equivalent only — fit can still vary by brand and style.
Fit note Use these as chart conversions, not guaranteed fit matches. If the band is close but not right, try a sister size before assuming the cup volume itself is wrong.
Bra Size Converter: international size chart and sister-size guide
Bra size conversion is one of those tasks that looks simple until labels from different markets stop lining up cleanly. This page converts common US, UK, EU, AU/NZ, FR/ES, IT, and JP bra sizes into equivalent chart labels, then adds sister-size guidance so you can see which nearby sizes may keep roughly the same cup volume when the band fit changes.
Why bra sizes do not convert perfectly
International bra labels are only chart equivalents. The same nominal size can still fit differently because brands grade bands and cups differently, wires vary, and cup shapes are not standardised. That is why a converter is useful for narrowing the search, but not enough to guarantee that two bras from different brands will fit the same way.
Cup letters are especially misleading when taken out of context because cup volume depends on the band. A 32C and a 38C are not the same cup volume. The letter only makes sense relative to the band, which is why conversion tools need to keep the band and cup together rather than treating the cup label as universal.
What sister sizes mean
Sister sizes are adjacent combinations that keep roughly the same cup volume while changing the band. If the band feels too tight but the cup volume feels close, going up one band and down one cup is usually the first thing to try. If the band feels too loose but the cup volume seems right, going down one band and up one cup is the usual move.
That is still only a fitting shortcut, not a guarantee. Sister sizes help when the volume feels close, but they do not fix all fit issues. Strap placement, cup height, wire width, and the overall shape of the bra can still make two nominally related sizes feel very different.
How to use an international bra-size converter
Start from the size system that best matches the bra you already know fits reasonably well. Convert that label across other systems to identify the likely equivalent starting size in the target market. Then use the sister sizes if the target bra feels right in cup volume but wrong in band tension.
This approach is especially helpful when switching between UK and EU-labelled bras, or when shopping a region where the band numbering changes more than the cup lettering. The converter gives you a chart starting point; the fitting decision still needs to be confirmed on the body.
Worked example: US 32C
A US 32C generally maps to UK 32C, EU 70C, AU/NZ 10C, FR/ES 85C, IT 2C, and JP 70C on a standard conversion chart. If the 32 band feels too firm but the cup volume feels close, the usual sister size up is 34B. If the band feels too loose but the cup volume feels close, the usual sister size down is 30D.
That example shows why the sister-size row matters. The direct international conversions tell you how the label changes between systems, while the sister-size guidance tells you what to try next if the label equivalent is close but not quite right in wear.
Frequently asked questions
Is a UK cup size the same as a US cup size?
Not always. The early part of the alphabet often looks similar, but UK systems keep using double-letter progression differently from many US charts once you move beyond D and DD. That is why the full size should be converted as one unit rather than by changing the band only.
What is a sister size in bras?
A sister size is a nearby size with roughly the same cup volume but a different band. One band up usually means one cup down, and one band down usually means one cup up. It is a practical fitting adjustment when the volume feels close but band tension does not.
Why can two bras with the same converted size still fit differently?
Because sizing charts are only label guides. Real fit also depends on brand grading, underwire width, cup depth, strap placement, padding, and fabric stretch. The converter gives a strong starting point, but brand and style variation still matters.
Should I trust the converter or the brand's own size chart?
Use the converter to get to the right neighbourhood, then check the brand's chart and fit notes for the final choice. The converter is best for translating labels across systems, while the brand chart is better for confirming how that brand intends to grade its sizes.
