Breast Size Comparison Tool

7 sizing systems25+ country calculatorsBands 28-60, cups AA-PZero data stored

Is a 32DD bigger than a 36B? Pick two sizes and this tool compares their estimated cup volumes, tells you which holds more and by roughly what percentage, and flags when the two are actually sister sizes holding the same volume under different labels.

The answers surprise most people, because cup letters only mean something relative to their band.

Size one (US)

Size two (US)

34C is roughly 113% larger in cup volume than 36B.

Estimated volumes: 34C ≈ 415 cc, 36B ≈ 195 cc. Volume model documented on the methodology section; real garments vary by cut.

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How the volume model works

Cup volume scales with two things: the bust-minus-band difference (the letter) and the frame it projects from (the band). Our model approximates each cup as a half-ellipsoid whose depth comes from the letter's inch difference and whose base scales with band size, calibrated against published volumetric fitting studies. It is deliberately simple and stated openly so the comparisons stay honest: real garments vary by cut, but the relative comparison between two sizes holds.

The famous consequence: a 30F holds less than a 38C. Letters read as big or small only after you attach the band, which is also why 'what cup size is she' questions have no meaningful answer without one.

Frequently asked questions

Is a D cup always bigger than a B cup?

Only on the same band. A 30D holds close to a 34B, and a 38B holds more than a 30D. The letter counts inches above the band, so the band decides what the letter means.

Which is bigger, 34DD or 36C?

They are almost identical in cup volume; they are sister sizes one step apart (34DD sisters to 36D... one letter beyond C). Precisely: 36C sisters to 34D, so a 34DD is about one letter larger than a 36C.

How accurate is cup volume estimation?

Good for relative comparison, approximate in absolute terms. Real cup capacity varies by construction and shape, so treat the cc figures as scaled estimates and the percentage comparison as the useful output.

Next steps

Last updated August 2026.