Check band, cups, centre and straps as separate fit variables; different constructions redistribute support differently.
Cup letters are relational
A cup letter does not describe one absolute volume independent of the band and sizing convention.
- Band conversion is often simpler than cup conversion.
- US cup notation is especially brand-dependent after D.
Step-by-step method
- 1
Start with the current size and confirm whether the retailer labels it UK or US.
- 2
Keep the band number separate from cup conversion.
- 3
Locate the cup step in the source system rather than matching letters visually.
- 4
Use the destination brand’s own cup sequence where possible.
- 5
Treat the converted label as a size to compare, then fit-check the real product.
Worked example
Example: a UK E cup and a US label at a comparable step may not share the same letter. The destination chart is the final naming authority.
Common mistakes that change the answer
- Assuming DD/DDD/E/F mean the same step in every US brand.
- Converting only the cup and forgetting the retailer may use a different regional chart.
- Treating the converted label as proof of identical cup geometry.
When the related tool helps
Use the calculator after you have confirmed the measurement method or product-specific chart. Arithmetic can be exact while the fit or care decision still depends on construction, brand rules or your personal reference garment.
Continue with the working tool
The related tool starts with blank inputs and keeps its assumptions visible.
Open related tool →Questions people ask
Is there one universal answer for every brand?
No. Use the method to narrow the decision, then verify the current product chart and construction.
What should I do if two clues conflict?
Prioritize direct measurement and observable fit, change one variable at a time, and compare the adjacent size or construction rather than forcing a generic rule.