Find Your Estimated Bra Size
Use a soft measuring tape and enter your snug underbust and fullest bust measurements. This tool gives a starting point, not a final fitting.
Measure around your ribcage, directly under your bust, with the tape level and snug.
Measure around the fullest part of your bust while standing naturally.
What this bra calculator does
A bra calculator helps you estimate two things: your band size and your cup size. It uses your underbust and full bust measurements to suggest a likely starting size (for example, 34C or 32DD/E). This is useful if you are shopping online or if your current bras feel uncomfortable.
How to measure for better accuracy
1) Measure your underbust
Place a measuring tape right under your bust and keep it level around your body. Keep the tape snug but not painfully tight. This number mainly determines your band size.
2) Measure your full bust
Measure around the fullest part of your bust, again keeping the tape level. Do not compress tissue with the tape. This number, compared against your band size, determines cup size.
3) Use your result as a starting point
Bra sizing is not perfectly standardized across brands. A 34C in one brand can fit differently than a 34C in another. Use the calculator result to narrow your options, then fine-tune by fit.
How cup sizing works
Cup letters are based on the difference between your bust measurement and your band size. As the difference increases, cup letters generally increase. A key point many people miss: cup size is relative to band size. That means a 32D and a 36D do not hold the same volume.
Sister sizes explained
Sister sizes are alternate sizes with similar cup volume. If your calculator result is close but not perfect, sister sizing can help:
- Go down one band size and up one cup size (example: 34C → 32D).
- Go up one band size and down one cup size (example: 34C → 36B).
This is useful when the band feels too tight or too loose, but cup volume seems close.
Common bra fit checks
- Band rides up: usually too loose; try a smaller band.
- Cups spill over: cups likely too small; go up in cup size.
- Cup gaping: cups may be too large or the style may not match your shape.
- Straps digging in: often a band/cup support issue, not just strap tightness.
- Center gore not tacking: cups may be too small or band too loose.
Final note
This bra size calculator gives an estimate based on standard sizing logic. For the best comfort and support, always try on bras when possible and adjust based on real-world fit. Body shape, breast root width, projection, and bra style all affect your final best size.