Using the Bra Size Calculator
Enter both circumferences in inches. The calculator rounds underbust to the nearest even band, then compares full bust with that band to choose a supported UK cup step. It does not convert to every brand's size system.
Worked example
Use the example inputs below to reproduce this result. These are the form's starting values, not recommended targets. Changing your inputs updates your result above; this worked example stays fixed for comparison. Results are rounded for display.
Example inputs
- Snug underbust (in)
- 32
- Full bust (in)
- 36
Example result
- UK starting size
- 32D
- Band (in)
- 32
- Bust minus band (in)
- 4
Method and assumptions
Rounds underbust to the nearest even band size, then uses inch differences for UK cup steps. Approximate fitting starting point; brands and sizing systems vary.
Use the size as a starting point
A size label compresses several fit considerations into a short code. It cannot capture every difference in shape, width or construction. Measure using the instructions associated with the product and compare the result with that manufacturer's chart. If the calculated label and the chart disagree, the product-specific information is more relevant to the purchase.
Common question
Can I use the cup letter directly in another country's sizing system?
Not reliably. Cup sequences and sizing conventions vary by market and brand. This tool reports a UK starting size; consult the specific brand's conversion and fitting information before translating the label into another system.
Guide updated .